Create Parent Hierarchy

Hello pedroccamaraDBI 

try this

let
Source = Excel.Workbook(File.Contents("C:\Users\Pedro\Desktop\Accounts.xlsx"), null, true),
Table1_Table = Source{[Item="Table1",Kind="Table"]}[Data],
#"Changed Type" = Table.TransformColumnTypes(Table1_Table,{{"GL SNC AccountID", type text}, {"GroupingCategory", type text}}),
BufferMaterial = List.Buffer(#"Changed Type"[GL SNC AccountID]),
AddParent = Table.AddColumn
(
#"Changed Type",
"Parent",
(row)=> List.Last(List.Select(List.Transform(BufferMaterial, (trans)=> if trans = Text.Start(row[GL SNC AccountID], Text.Length(trans)) and trans<> row[GL SNC AccountID] then trans else null),each _<> null))
)
in
AddParent

Copy paste this code to the advanced editor in a new blank query to see how the solution works.

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Kudoes are nice too

Have fun

Jimmy