Generate a Custom Navigation Table with List.Generate

Here is a proof of concept for the child level

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WclTSUTJUitWBsIzgLGM4ywTMcgKpM0AwDRFMIwTTGMFE0maqFBsLAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t, Column2 = _t]),
    #"Added Custom" = Table.AddColumn(Source, "Custom", each #table({"Name","Key","Data","ItemKind","ItemName","IsLeaf"},{{[Column2],{[Column2]},"your function here " & [Column2],"Table",[Column2],true}})),
    #"Grouped Rows" = Table.Group(#"Added Custom", {"Column1"}, {{"Group", each _, type table [Custom=table]}}),
    #"Added Custom1" = Table.AddColumn(#"Grouped Rows", "Children", each Table.Combine([Group][Custom]))
in
    #"Added Custom1"

You would still need to call the NavTable function on the "Children"  tables and then on the "Column1"  tables to tie it together, but you can already see the dynamic approach.