Index multiple subgroups

JulieCooper if your data is properly sorted then this should work (w/o Table.Group). If not sorted - sort them first. 

let
    s = your_table,
    rows = List.Buffer(Table.ToRows(s)),
    cost_types = [SC = "1", LB = "2", MT = "3", PL = "4", OT = "5", SM = "6", RV = "7"],
    func = (prev, curr) => 
        curr & 
        {prev{4} + Number.From(prev{0} <> curr{0}),
        if prev{0} = curr{0} then prev{5} + Number.From(prev{1} <> curr{1}) else 1,
        if curr{2} = null then 0 else if {prev{0}, prev{1}} <> {curr{0}, curr{1}} then 1 else prev{6} + 1,
        Record.FieldOrDefault(cost_types, curr{3}, null)}, 
    gen = List.Generate(
        () => [i = 0, c = rows{0} & {1, 1, if rows{0}{2} = null then 0 else 1, Record.FieldOrDefault(cost_types, rows{0}{3}, null)}],
        (x) => x[i] < List.Count(rows),
        (x) => [i = x[i] + 1, c = func(x[c], rows{i})],
        (x) => x[c]
    ),
    tbl = Table.FromRows(gen, Table.ColumnNames(s) & {"Header Code", "Subheader Code", "Item Code", "Cost Type Code"}),
    cubit = Table.AddColumn(
        tbl, 
        "Cubit Code", 
        (x) => Text.From(x[Header Code]) & Number.ToText(x[Subheader Code], "00") &
            Number.ToText(x[Item Code], "00") & Text.From(x[Cost Type Code]) & x[Cost Type]
    )
in
    cubit