С данными в столбцах A и B , попробуйте этот короткий макрос:
Sub SplitList()
Dim i As Long, j As Long, N As Long
Dim v As String, arr, a
N = Cells(Rows.Count, "A").End(xlUp).Row
j = 1
For i = 1 To N
v = Cells(i, 1).Value
arr = Split(Cells(i, 2).Value, ",")
For Each a In arr
Cells(j, 3).Value = v
Cells(j, 4).Value = a
j = j + 1
Next a
Next i
End Sub
Вывод в столбцах C и D .