Excel Dynamic Grouping/Hierarchy Tool With Merged Rows

I commonly use sheets that look like the following:

That is built as a comparison tool based on exports from another application. Note that the rows are merged 2 at a time.

The number in left-most column is currently being used for conditional formatting to add the coloring, but it also represents the hierarchy that I am trying to group by.

As it currently stands, I go through and manually group the rows so that they can be expanded and collapsed. My goal is to figure out a way to use VBA to do that work for me since these sheets can often be 5,000+ rows.

I've found similar threads that get me close, but I haven't figured out a way to make it work with merged rows like shown, the closest I have been able to get is grouping just the first row but not grabbing both.

Any help is greatly appreciated! Thanks!

I'm not a real user of grouping in Excel, so I might be misunderstanding your use case, but this seemed to work for me on a simple example:

Sub GroupIt()
    Dim ws As Worksheet, c As Range, grp As Range
    Dim rngLevels As Range, lvl As Long, maxLvl As Long, i As Long
    
    Set ws = ActiveSheet
    ws.Cells.ClearOutline               'clear previous grouping
    Set rngLevels = ws.Range("A2:A33")  'range with the level values
    maxLvl = Application.Max(rngLevels) 'max level value
    Debug.Print maxLvl
    Application.ScreenUpdating = False
    For lvl = maxLvl To 2 Step -1       'loop down from max. level
        Set grp = Nothing
        For Each c In rngLevels.Cells
            If c.MergeArea(1).Value >= lvl Then   'current level or greater?
                UnionRanges grp, c      'add this row to the current group
            Else
                CloseGroup grp          'group any collected rows
            End If
        Next c
        CloseGroup grp
    Next lvl
    
End Sub

'Handle closing out a group of collected cells and
'   reset `grp` to Nothing
Sub CloseGroup(ByRef grp As Range)
    If Not grp Is Nothing Then
        Debug.Print "Grouping " & grp.Address
        grp.EntireRow.Group
        Set grp = Nothing
    End If
End Sub

'Add range `rngToadd` to range `RngTot`
Sub UnionRanges(rngTot As Range, rngToAdd As Range)
    If rngTot Is Nothing Then
        Set rngTot = rngToAdd
    Else
        Set rngTot = Application.Union(rngTot, rngToAdd)
    End If
End Sub

Before and after: