How to make lists of all possible combinations in VBA, with variable sized lists

Use an array sized for the number of lines. Increment each element within the bounds of the number of elements of that line. For example a 1D array of 4 elements ar(3). ar(0) increments 0 to 3 (a,b,c,d), ar(1) is 0 to 1 (e,f), ar(2) is 0 to 2 (g,h,i) and ar(3) is 0 to 4 (l,m,n,o,p). Array arN holds for the number of element for a line.

Option Explicit

Sub combinations()

    Dim n As Long, t As Long
    Dim i As Long, j As Long, s As String
    Dim arIn, ar, arN, arSeq
    
    With Sheet1
        ' list in A1:A4
        
        arIn = .Range("A1:A4").Value2
        
        ' determine array sizes
        n = UBound(arIn) - 1
        ReDim arSeq(n)
        ReDim arN(n)
        
        ' fill arrays
        For i = 0 To n
           s = Replace(arIn(i + 1, 1), " ", "")
           arSeq(i) = Split(s, ",")
           arN(i) = UBound(arSeq(i))
        Next
    End With
    
    ' calc total combinations
    t = 1
    For n = 0 To UBound(arN)
       t = t * (arN(n) + 1)
    Next
    MsgBox "Permutations=" & t
   
    ' start at
    ar = Array(0, 0, 0, 0)
    
    ' output results
    With Sheet1
        For j = 1 To t
            For i = 0 To UBound(ar)
                .Cells(i + 1, j + 1) = arSeq(i)(ar(i))
            Next
            ' next sequence
            Call incr(ar, arN)
        Next
    End With

End Sub

Sub incr(ByRef ar, arN)

    Dim i As Long, n As Long
     
    ' increment LH digit
    n = UBound(ar)
    ar(n) = ar(n) + 1
    
    ' check carry overs
    For i = n To 0 Step -1
        If ar(i) > arN(i) Then
            If i = 0 Then
                ' no more
                MsgBox "End"
                End
            End If
            ar(i) = 0
            ' increment prev digit
            ar(i - 1) = ar(i - 1) + 1
        Else
            Exit Sub
        End If
     Next
End Sub