Getting all child values for every parent value based on a column

Hi rp2022, another solution:

(Parent and Child columns must be as text so ChangedType step is important)

Output:

let
    Source = Expression.Evaluate("Table.FromRows(List.Transform(Text.Split(""1;3;E|2;102;F|3;5;F|3;4;E|4;6;E|7;170;F|8;9;E|9;10;E|10;11;E|11;110;F|12;120;F|13;14;E|14;140;F|15;16;E|16;160;F|17;18;E|18;19;E|19;20;E|21;20;E|20;200;F"",""|""), each Text.Split(_, "";"")), {""Parent"",""Child"",""Type""})", #shared),
    ChangedType = Table.TransformColumnTypes(Source,{{"Parent", type text}, {"Child", type text}, {"Type", type text}}),

    Grouped = Table.Group(ChangedType, {"Parent"}, {{"T", each _, type table}}),
    R = Function.Invoke(Record.FromList, List.Reverse(Table.ToColumns(Grouped))),
    F = (parent)=>
    Table.Combine(List.Generate(
        ()=> [ par = Text.From(parent), t = Record.FieldOrDefault(R, par, #table(null, {})) ],
        each not Table.IsEmpty([t]),
        each [ par = [t][Child], t = Table.Combine(List.Transform(par, (r)=> Record.FieldOrDefault(R, r, #table(null, {})))) ],
        each [t])),
    Result = F(8)
in
    Result