Macro/Formula | Add n Rows and Transpose n Columns to Single Column

This code should do the job. Please paste it to a standard code module.

Sub Format_BOM()
    ' Variatus @TeachExcel 20 Feb 2020
    
    Dim Ws As Worksheet
    Dim Tbl As ListObject
    Dim Arr As Variant
    Dim R As Long, C As Long
    
    Set Ws = Worksheets("Start (2)")        ' change to suit
    ' this presumes that there is only one table in Ws
    Set Tbl = Ws.ListObjects(1)
    Application.ScreenUpdating = False
    
    Tbl.ShowTableStyleRowStripes = False
    With Tbl.DataBodyRange
        For R = .Rows.Count To 1 Step -1
            C = WorksheetFunction.CountA(.Rows(R))
            If C > 1 Then
                Arr = .Rows(R).Value
                ReDim Preserve Arr(1 To 1, 1 To WorksheetFunction.CountA(.Rows(R)))
                
                For C = UBound(Arr, 2) To 2 Step -1
                    Tbl.ListRows.Add (R + 1)
                    .Cells(R + 1, 1).Value = Arr(1, 1)
                    .Cells(R + 1, 2).Value = Arr(1, C)
                Next C
            End If
        Next R
    End With
    
    ApplyRowColor
    With Application
        .ScreenUpdating = True
        .StatusBar = "All done"
    End With
End Sub

Sub ApplyRowColor()

    Dim Arr As Variant
    Dim R As Long
    
    With ActiveSheet.ListObjects(1).DataBodyRange
        .Interior.Pattern = xlNone
        Arr = .Columns(1).Value
        For R = 1 To UBound(Arr)
            On Error Resume Next
            If Arr(R, 1) <> Arr(R - 1, 1) Then
                .Rows(R).Interior.Color = 13561798
            End If
        Next R
    End With
End Sub

The procedure is installed in the attached workbook. Let me know if you need further help.

Edit Feb 20, 2020   ===============================

There were some inaccuracies in my original post dated Feb 14. These have been resolved. The attachment was replaced. In the new version row coloring is applied in a separate procedure which can also be called independently to apply row coloring to sheets which have been formatted previously.