How do I make this loop all children recursively?

Hi v-yanjiang-msft , thx for your suggestion. So  I tried to create a custom function "SubChilldren" with List.Generate()

(children as text, ColChild,ColParent,source)=>
let 
i = 1,
length = Text.Length(children),

subchildren =  List.Generate( ()=>@flecheD(ColChild,ColParent,Text.At(children,i-1),source),   i<=length, i+1  )
in 
Text.Combine(subchildren)

which when coupled with my initial function

(ColChild,ColParent,ParentActuel,source)=>
                    let
                    mylist=Table.Column(Table.SelectRows(source,each Record.Field(_,ColParent)=ParentActuel),ColChild),
                    resultat=Text.Combine(mylist)
                    in
                   
                   Text.Trim(
                    if resultat ="" then ""  else if Text.Length(resultat) = 1 then  @ resultat &"|" & @ flecheD(ColChild,ColParent,resultat,source)
                    else     @resultat &"|"& SubChildren(resultat,ColChild,ColParent,source),"|")

  should normally get the sub-children  of each children. However, it still doesnt work 😅. Could you please help me . Thx

source link : https://docs.google.com/spreadsheets/d/1nbF7-ZBZNMCmHdzSqqfBdHCPNqdWfKGa/edit?usp=sharing&ouid=104317018191542815438&rtpof=true&sd=true 

@Gop01