diff --git a/applications/test/CompactListList/Make/files b/applications/test/CompactListList/Make/files
index 7b7e043c6e..79a127a7be 100644
--- a/applications/test/CompactListList/Make/files
+++ b/applications/test/CompactListList/Make/files
@@ -1,3 +1,3 @@
-Test-CompactListList.C
+Test-CompactListList.cxx
 
 EXE = $(FOAM_USER_APPBIN)/Test-CompactListList
diff --git a/applications/test/CompactListList/Test-CompactListList.C b/applications/test/CompactListList/Test-CompactListList.cxx
similarity index 90%
rename from applications/test/CompactListList/Test-CompactListList.C
rename to applications/test/CompactListList/Test-CompactListList.cxx
index 45d45e0996..080adf25f3 100644
--- a/applications/test/CompactListList/Test-CompactListList.C
+++ b/applications/test/CompactListList/Test-CompactListList.cxx
@@ -38,6 +38,8 @@ Description
 #include "SpanStream.H"
 #include "faceList.H"
 
+#include <iterator>  // for back_inserter
+
 using namespace Foam;
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
@@ -161,6 +163,25 @@ int main(int argc, char *argv[])
         faceList fcs2 = compactFcs.unpack<face>();
         Info<< "deserialized:" << fcs2 << endl;
 
+        // Unpack some faces
+        DynamicList<face> extracted(compactFcs.size());
+
+        compactFcs.copy_unpack<face>
+        (
+            std::back_inserter(extracted),
+            2, 2
+        );
+
+        Info<< "copy_unpack 1: " << extracted << nl;
+
+        compactFcs.copy_unpack<face>
+        (
+            std::back_inserter(extracted)
+            // labelRange(2, 1)
+        );
+
+        Info<< "copy_unpack 2: " << extracted << nl;
+
         // From some faces
         IndirectList<face> subfaces(fcs, labelList({2, 4, 1}));
 
diff --git a/applications/test/globalIndex/Make/files b/applications/test/globalIndex/Make/files
deleted file mode 100644
index ba9900cd82..0000000000
--- a/applications/test/globalIndex/Make/files
+++ /dev/null
@@ -1,3 +0,0 @@
-Test-globalIndex.C
-
-EXE = $(FOAM_USER_APPBIN)/Test-globalIndex
diff --git a/applications/test/globalIndex/Make/options b/applications/test/globalIndex/Make/options
deleted file mode 100644
index 90f18e878f..0000000000
--- a/applications/test/globalIndex/Make/options
+++ /dev/null
@@ -1 +0,0 @@
-EXE_INC = /* -DFULLDEBUG -g -O0 */
diff --git a/applications/test/globalIndex1/Make/files b/applications/test/globalIndex1/Make/files
new file mode 100644
index 0000000000..109f344340
--- /dev/null
+++ b/applications/test/globalIndex1/Make/files
@@ -0,0 +1,3 @@
+Test-globalIndex1.cxx
+
+EXE = $(FOAM_USER_APPBIN)/Test-globalIndex1
diff --git a/applications/test/globalIndex1/Make/options b/applications/test/globalIndex1/Make/options
new file mode 100644
index 0000000000..18e6fe47af
--- /dev/null
+++ b/applications/test/globalIndex1/Make/options
@@ -0,0 +1,2 @@
+/* EXE_INC = */
+/* EXE_LIBS = */
diff --git a/applications/test/globalIndex/Test-globalIndex.C b/applications/test/globalIndex1/Test-globalIndex1.cxx
similarity index 98%
rename from applications/test/globalIndex/Test-globalIndex.C
rename to applications/test/globalIndex1/Test-globalIndex1.cxx
index a33bccc6d1..6fbc328707 100644
--- a/applications/test/globalIndex/Test-globalIndex.C
+++ b/applications/test/globalIndex1/Test-globalIndex1.cxx
@@ -25,7 +25,7 @@ License
     along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
 
 Application
-    globalIndexTest
+    Test-globalIndex1
 
 Description
     Simple tests for the globalIndex class.
@@ -53,7 +53,7 @@ int main(int argc, char *argv[])
     #include "createPolyMesh.H"
 
     // Global numbering of cells (proc0 elements first, then proc1, etc.)
-    globalIndex globalNumbering(mesh.nCells());
+    const globalIndex globalNumbering(mesh.nCells());
 
     Pout<< "local-offset: " << globalIndex::calcOffset(mesh.nCells()) << nl;
     Pout<< "local-range: " << globalIndex::calcRange(mesh.nCells()) << nl;
@@ -185,7 +185,7 @@ int main(int argc, char *argv[])
 
 
     // Get a few cell indices
-    const label nTotalCells = globalNumbering.size();
+    const label nTotalCells = globalNumbering.totalSize();
 
     Random rndGen(UPstream::myProcNo());
     DynamicList<label> globalIDs;
diff --git a/applications/test/globalIndex2/Make/files b/applications/test/globalIndex2/Make/files
new file mode 100644
index 0000000000..6e167d65ac
--- /dev/null
+++ b/applications/test/globalIndex2/Make/files
@@ -0,0 +1,3 @@
+Test-globalIndex2.cxx
+
+EXE = $(FOAM_USER_APPBIN)/Test-globalIndex2
diff --git a/applications/test/globalIndex2/Make/options b/applications/test/globalIndex2/Make/options
new file mode 100644
index 0000000000..18e6fe47af
--- /dev/null
+++ b/applications/test/globalIndex2/Make/options
@@ -0,0 +1,2 @@
+/* EXE_INC = */
+/* EXE_LIBS = */
diff --git a/applications/test/globalIndex2/Test-globalIndex2.cxx b/applications/test/globalIndex2/Test-globalIndex2.cxx
new file mode 100644
index 0000000000..a8bd73c394
--- /dev/null
+++ b/applications/test/globalIndex2/Test-globalIndex2.cxx
@@ -0,0 +1,95 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2023 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Application
+    Test-globalIndex2
+
+Description
+    More functional tests for the globalIndex class.
+
+\*---------------------------------------------------------------------------*/
+
+#include "globalIndex.H"
+#include "argList.H"
+#include "Time.H"
+#include "IOstreams.H"
+#include "Random.H"
+#include "IndirectList.H"
+#include "SliceList.H"
+
+using namespace Foam;
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+//  Main program:
+
+int main(int argc, char *argv[])
+{
+    Random rnd(123456);
+
+    // #include "setRootCase.H"
+    // #include "createTime.H"
+
+    Info<< nl
+        << "simple globalIndex tests" << nl << nl;
+
+    Info<< "Construct from indirect list(s)" << nl;
+    {
+        // Some sizes
+        labelList rawSizes(25);
+        forAll(rawSizes, i)
+        {
+            rawSizes[i] = rnd.position<label>(0, 100);
+        }
+
+        Info<< nl
+            << "plain sizes: "
+            << flatOutput(rawSizes) << nl
+            << "    offsets: "
+            << flatOutput(globalIndex::calcOffsets(rawSizes))
+            << nl;
+
+
+        sliceRange slice(0, 5, 5);
+        Info<< nl
+            << "range min/max " << slice.min() << '/' << slice.max() << nl;
+
+        SliceList<label> sliceSizes(rawSizes, slice);
+
+        Info<< nl
+            << "indirect addr: " << sliceSizes.addressing() << nl
+            << "indirect sizes: "
+            << flatOutput(sliceSizes) << nl
+            << "       offsets: "
+            << flatOutput(globalIndex::calcOffsets(sliceSizes))
+            << nl;
+    }
+
+    Info<< "\nEnd\n" << endl;
+    return 0;
+}
+
+
+// ************************************************************************* //
diff --git a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.C b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.C
index 1dcd12b86c..cf45130667 100644
--- a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.C
+++ b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.C
@@ -393,6 +393,72 @@ void Foam::CompactListList<T>::transfer
 }
 
 
+template<class T>
+template<class SubListType, class OutputIter>
+OutputIter Foam::CompactListList<T>::copy_unpack
+(
+    OutputIter d_iter,
+    const label pos,
+    label len
+) const
+{
+    if (pos >= 0 && pos < this->size())
+    {
+        // Change sub-length to (one-past) end position
+        // len == -1 (like std::string::npos) - search until end
+
+        if (len > 0) len += pos;
+        if (len < 0 || len > this->size())
+        {
+            len = this->size();
+        }
+
+        for (label i = pos; i < len; ++i)
+        {
+            *d_iter = SubListType(this->localList(i));
+            ++d_iter;
+        }
+    }
+
+    return d_iter;
+}
+
+
+template<class T>
+template<class SubListType, class OutputIter>
+OutputIter Foam::CompactListList<T>::copy_unpack
+(
+    OutputIter d_iter,
+    const labelRange& range
+) const
+{
+    return this->copy_unpack<SubListType>(d_iter, range.start(), range.size());
+}
+
+
+template<class T>
+template<class SubListType, class OutputIter>
+OutputIter Foam::CompactListList<T>::copy_unpack
+(
+    OutputIter d_iter,
+    const labelUList& indices
+) const
+{
+    for (label i : indices)
+    {
+        *d_iter = SubListType(this->localList(i));
+        ++d_iter;
+    }
+
+    return d_iter;
+}
+
+
+// Could also support copy_unpack() with IndirectListBase, as required...
+// or the caller can also just use copy_unpack with len = 1 and the
+// desired position
+
+
 template<class T>
 template<class SubListType>
 Foam::List<SubListType>
@@ -400,10 +466,7 @@ Foam::CompactListList<T>::unpack() const
 {
     List<SubListType> lists(size());
 
-    forAll(lists, i)
-    {
-        lists[i] = SubListType(this->localList(i));
-    }
+    this->copy_unpack<SubListType>(lists.begin());
 
     return lists;
 }
@@ -416,16 +479,24 @@ Foam::CompactListList<T>::unpack(const labelRange& range) const
 {
     List<SubListType> lists(range.size());
 
-    auto iter = lists.begin();
-
-    for (const label i : range)
-    {
-        *iter = SubListType(this->localList(i));
-        ++iter;
-    }
+    this->copy_unpack<SubListType>(lists.begin(), range.start(), range.size());
 
     return lists;
 }
 
 
+template<class T>
+template<class SubListType>
+Foam::List<SubListType>
+Foam::CompactListList<T>::unpack(const labelUList& indices) const
+{
+    List<SubListType> lists(indices.size());
+
+    this->copy_unpack<SubListType>(lists.begin(), indices);
+
+    return lists;
+}
+
+
+
 // ************************************************************************* //
diff --git a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.H b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.H
index a912bb5767..3401179116 100644
--- a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.H
+++ b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListList.H
@@ -319,18 +319,6 @@ public:
         void setLocalSize(const label rowi, const label len);
 
 
-        //- Redimension - same as resize()
-        inline void setSize(const label mRows);
-
-        //- Redimension - same as resize()
-        inline void setSize(const label mRows, const label nVals);
-
-        //- Redimension - same as resize()
-        inline void setSize(const label mRows, const label nVals, const T&);
-
-        //- Reset sizes - same as resize()
-        inline void setSize(const labelUList& listSizes);
-
         //- Swap contents
         void swap(CompactListList<T>& other);
 
@@ -358,6 +346,49 @@ public:
 
     // Pack / Unpack
 
+        //- Unpack sub-list copies in the range defined by \p pos and \p len
+        //- with bounding behaviour like List::slice() by copy constructing
+        //- begin at the destination iterator \p d_iter.
+        //
+        // \returns Output iterator to the element in the destination range,
+        //  one past the last element copied.
+        template<class SubListType, class OutputIter>
+        OutputIter copy_unpack
+        (
+            //! [out] The output destination
+            OutputIter d_iter,
+            //! The start of sub-region to copy (no-op if -ve or out-of-range)
+            const label pos = 0,
+            //! The length of sub-region to copy (-ve = until the end)
+            label len = -1
+        ) const;
+
+        //- Unpack sub-list copies in the specified range.
+        //
+        // \returns Output iterator to the element in the destination range,
+        //  one past the last element copied.
+        template<class SubListType, class OutputIter>
+        OutputIter copy_unpack
+        (
+            //! [out] The output destination
+            OutputIter d_iter,
+            //! The sub-region to copy
+            const labelRange& range
+        ) const;
+
+        //- Unpack sub-list copies for the specified indices
+        //
+        // \returns Output iterator to the element in the destination range,
+        //  one past the last element copied.
+        template<class SubListType, class OutputIter>
+        OutputIter copy_unpack
+        (
+            //! [out] The output destination
+            OutputIter d_iter,
+            //! The sub-regions to copy
+            const labelUList& indices
+        ) const;
+
         //- Return non-compact list of lists
         template<class SubListType = List<T>>
         List<SubListType> unpack() const;
@@ -366,6 +397,10 @@ public:
         template<class SubListType = List<T>>
         List<SubListType> unpack(const labelRange& range) const;
 
+        //- Return non-compact list of lists for specified indices
+        template<class SubListType = List<T>>
+        List<SubListType> unpack(const labelUList& indices) const;
+
 
     // Assignment
 
@@ -443,11 +478,11 @@ public:
     // Housekeeping
 
         //- Const access to the packed values
-        //FOAM_DEPRECATED_STRICT(2022-03, "values()")
+        FOAM_DEPRECATED_STRICT(2022-03, "values()")
         const List<T>& m() const noexcept { return values_; }
 
         //- Non-const access to the packed values
-        //FOAM_DEPRECATED_STRICT(2022-03, "values()")
+        FOAM_DEPRECATED_STRICT(2022-03, "values()")
         List<T>& m() noexcept { return values_; }
 
         //- Return flat index into packed values
@@ -461,6 +496,30 @@ public:
         {
             return this->toLocal(rowi, i);
         }
+
+        //- Redimension - same as resize()
+        void setSize(const label mRows)
+        {
+            this->resize(mRows);
+        }
+
+        //- Redimension - same as resize()
+        void setSize(const label mRows, const label nVals)
+        {
+            this->resize(mRows, nVals);
+        }
+
+        //- Redimension - same as resize()
+        void setSize(const label mRows, const label nVals, const T& val)
+        {
+            this->resize(mRows, nVals, val);
+        }
+
+        //- Reset sizes - same as resize()
+        void setSize(const labelUList& listSizes)
+        {
+            this->resize(listSizes);
+        }
 };
 
 
diff --git a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListI.H b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListI.H
index 969bc0d0af..f5a17ba86d 100644
--- a/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListI.H
+++ b/src/OpenFOAM/containers/CompactLists/CompactListList/CompactListListI.H
@@ -364,12 +364,10 @@ inline void Foam::CompactListList<T>::resize(const label mRows)
     }
     else if (mRows > size())
     {
-        // Grow
-        FatalErrorInFunction
-            << "Cannot be used to extend the list from " << size()
-            << " to " << mRows << nl
-            << "    Please use a different resize() function"
-            << abort(FatalError);
+        // Extend number of rows, each with local size of 0
+        const label endOffset = offsets_.empty() ? 0 : offsets_.back();
+
+        offsets_.resize(mRows+1, endOffset);
     }
 }
 
@@ -381,9 +379,17 @@ inline void Foam::CompactListList<T>::resize
     const label nVals
 )
 {
-    offsets_.resize(mRows+1, Zero);
-    values_.resize(nVals);
-    // Optionally: enforceSizeSanity();
+    if (mRows < 1)
+    {
+        // Enforce sizing sanity
+        offsets_.clear();
+        values_.clear();
+    }
+    else
+    {
+        offsets_.resize(mRows+1, Zero);
+        values_.resize(nVals);
+    }
 }
 
 
@@ -394,9 +400,17 @@ inline void Foam::CompactListList<T>::resize_nocopy
     const label nVals
 )
 {
-    offsets_.resize(mRows+1, Zero);
-    values_.resize_nocopy(nVals);
-    // Optionally: enforceSizeSanity();
+    if (mRows < 1)
+    {
+        // Enforce sizing sanity
+        offsets_.clear();
+        values_.clear();
+    }
+    else
+    {
+        offsets_.resize(mRows+1, Zero);
+        values_.resize_nocopy(nVals);
+    }
 }
 
 
@@ -408,49 +422,17 @@ inline void Foam::CompactListList<T>::resize
     const T& val
 )
 {
-    offsets_.resize(mRows+1, Zero);
-    values_.resize(nVals, val);
-    // Optionally: enforceSizeSanity();
-}
-
-
-template<class T>
-inline void Foam::CompactListList<T>::setSize(const label mRows)
-{
-    this->resize(mRows);
-}
-
-
-template<class T>
-inline void Foam::CompactListList<T>::setSize
-(
-    const label mRows,
-    const label nVals
-)
-{
-    this->resize(mRows+1, nVals);
-}
-
-
-template<class T>
-inline void Foam::CompactListList<T>::setSize
-(
-    const label mRows,
-    const label nVals,
-    const T& val
-)
-{
-    this->resize(mRows+1, nVals, val);
-}
-
-
-template<class T>
-inline void Foam::CompactListList<T>::setSize
-(
-    const labelUList& listSizes
-)
-{
-    this->resize(listSizes);
+    if (mRows < 1)
+    {
+        // Enforce sizing sanity
+        offsets_.clear();
+        values_.clear();
+    }
+    else
+    {
+        offsets_.resize(mRows+1, Zero);
+        values_.resize(nVals, val);
+    }
 }
 
 
diff --git a/src/OpenFOAM/parallel/globalIndex/globalIndex.C b/src/OpenFOAM/parallel/globalIndex/globalIndex.C
index bfbaa6cc80..8f314ba328 100644
--- a/src/OpenFOAM/parallel/globalIndex/globalIndex.C
+++ b/src/OpenFOAM/parallel/globalIndex/globalIndex.C
@@ -336,6 +336,19 @@ Foam::globalIndex::bin
 }
 
 
+void Foam::globalIndex::resize(const label n)
+{
+    if (n < 1)
+    {
+        offsets_.clear();
+    }
+    else
+    {
+        offsets_.resize(n+1, end_value());
+    }
+}
+
+
 void Foam::globalIndex::reset
 (
     const label localSize,
diff --git a/src/OpenFOAM/parallel/globalIndex/globalIndex.H b/src/OpenFOAM/parallel/globalIndex/globalIndex.H
index 19f6d04bf9..4656e94396 100644
--- a/src/OpenFOAM/parallel/globalIndex/globalIndex.H
+++ b/src/OpenFOAM/parallel/globalIndex/globalIndex.H
@@ -257,6 +257,10 @@ public:
         //- Reset to be empty (no offsets)
         inline void clear();
 
+        //- Change the number of entries (nProcs) in the offsets table.
+        //- Extending will fill with empty local sizes.
+        void resize(const label n);
+
         //- Reset from local size, using gather/broadcast
         //- with default/specified communicator if parallel.
         void reset
@@ -512,6 +516,15 @@ public:
             const bool checkOverflow = false
         );
 
+        //- Calculate offsets from an indirect list of local sizes,
+        //- with optional check for label overflow
+        template<class Addr>
+        static labelList calcOffsets
+        (
+            const IndirectListBase<label, Addr>& counts,
+            const bool checkOverflow = false
+        );
+
         //- Calculate offsets from list of lists,
         //- with optional check for label overflow
         template<class SubListType>
diff --git a/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C b/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
index 3643b21850..3898913fe9 100644
--- a/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
+++ b/src/OpenFOAM/parallel/globalIndex/globalIndexTemplates.C
@@ -30,6 +30,42 @@ License
 
 // * * * * * * * * * * * * * Static Member Functions * * * * * * * * * * * * //
 
+template<class Addr>
+Foam::labelList
+Foam::globalIndex::calcOffsets
+(
+    const IndirectListBase<label, Addr>& counts,
+    const bool checkOverflow
+)
+{
+    labelList values;
+
+    const label len = counts.size();
+
+    if (len)
+    {
+        values.resize(len+1);
+
+        label start = 0;
+        for (label i = 0; i < len; ++i)
+        {
+            const label count = counts[i];
+
+            values[i] = start;
+            start += count;
+
+            if (checkOverflow && start < values[i])
+            {
+                reportOverflowAndExit(i, values[i], count);
+            }
+        }
+        values[len] = start;
+    }
+
+    return values;
+}
+
+
 template<class SubListType>
 Foam::labelList
 Foam::globalIndex::calcListOffsets