help needed with unpivot columns

Somethign like this:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCg82MDBU0lFSitWJVgIxHMEsIyDLCcwyBrKcwSyQUiNkpS5wpa5wpW5wpcbISt3hSj3gSj2VYmMB", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Code = _t, Name = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Code", type text}, {"Name", type text}}),
   
   
    trig = (n) => Text.StartsWith(n[Code], "WS"),
    keep = {"Code", "Name"},

     f = (t as table, trigger as function, keepCols as list) =>
        let 
            tbl = Table.Buffer(t), //Consider removal if the code runs slow//
            Pivot = List.Accumulate(Table.ToRecords(tbl), {}, (a, n)=> if  trig(n)
                                                                        then 
                                                                            {Record.SelectFields(n, keepCols) & [Nested = {[]}]} & a 
                                                                        else 
                                                                            {Record.SelectFields(List.First(a), keepCols) & [Nested = List.First(a)[Nested] & {n}]} & List.Skip(a)),
            Extract = Table.FromRecords(Pivot),
            Convert = Table.TransformColumns(Extract,{{"Nested", each Table.FromRecords(List.Skip(_))}})
        in Convert,
  

    out = f(#"Changed Type", trig, keep),
    #"Expanded Nested" = Table.ExpandTableColumn(out, "Nested", {"Code", "Name"}, {"Nested.Code", "Nested.Name"})
in #"Expanded Nested"

Copy f funciton to your query and then call it in the way demonstrated in the out step.Kind regards,

John