Editing BOM automatically

Instead of

If Cells(x, 1).Value <> Cells(x + 1, 1).Value Then
 Rows(x + 1).select
      
 Selection.Insert Shift:=xlDown, CopyOrigin:=xlFormatFromLeftOrAbove
 Selection.Insert Shift:=xlDown, CopyOrigin:=xlFormatFromLeftOrAbove

you can use:

 
If Cells(x, 1).Value <> Cells(x + 1, 1).Value Then
  Rows(x + 1).Resize(2).Insert

But if adding a simple column:

Private Sub test()
 sn = Cells(1).CurrentRegion.Resize(, 1).Offset(, 9)
 sq = Cells(1).CurrentRegion.Offset(, 1).Resize(, 5)
 sq(1, 1) = 0
   
 For j = 3 To UBound(sn) - 1
  sq(1, 1) = sq(1, 1) + sq(j, 1)
   
  If sq(j, 5) <> sq(j + 1, 5) Then
   sn(j, 1) = sq(1, 1)
   sq(1, 1) = 0
   j = j + 1
  End If
 Next
   Cells(1, 9).Resize(UBound(sn)) = sn
End Sub