Formatting Rows and Columns in Large Spreadsheet

You may try the following formula-

=REDUCE({"Pledge ID","Payment ID"},TOCOL(DROP(A.:.A,1)&"|"&DROP(B.:.D,1),1),LAMBDA(a,x,VSTACK(a,TEXTSPLIT(x,"|"))))

How about VBA Macro:

Sub NormalizePledgePayments()
    Dim ws As Worksheet
    Set ws = ActiveSheet

    Dim lastRow As Long, lastCol As Long, outputRow As Long
    lastRow = ws.Cells(ws.Rows.Count, 1).End(xlUp).Row
    lastCol = ws.Cells(1, ws.Columns.Count).End(xlToLeft).Column

    Dim i As Long, j As Long
    outputRow = 1
    Sheets.Add.Name = "Normalized"

    For i = 2 To lastRow
        For j = 2 To lastCol
            If ws.Cells(i, j).Value <> "" Then
                With Sheets("Normalized")
                    .Cells(outputRow, 1).Value = ws.Cells(i, 1).Value
                    .Cells(outputRow, 2).Value = ws.Cells(i, j).Value
                End With
                outputRow = outputRow + 1
            End If
        Next j
    Next i
End Sub