An alternative could be Power Query which is available in legacy Excel such as Excel 2013.

let
    Source = Excel.CurrentWorkbook(){[Name="Tabelle2"]}[Content],
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Level", Int64.Type}, {"Item Number", type text}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "User Column", each if [Level] = 0 then [Item Number] else null),
    #"Filled Down" = Table.FillDown(#"Added Custom",{"User Column"}),
    #"Removed Duplicates" = Table.Distinct(#"Filled Down", {"Item Number", "User Column"}),
    #"Removed Columns" = Table.RemoveColumns(#"Removed Duplicates",{"User Column"})
in
    #"Removed Columns"