Get all combined subDirectories with Folder.Contents() from multiple servers (mainDirectories),

Remember that the Folder connector gives you all folder names for free.

let
    Source = Folder.Files("\\192.168.3.8\pi"),
    #"Removed Other Columns" = Table.SelectColumns(Source,{"Folder Path"}),
    #"Removed Duplicates" = Table.Distinct(#"Removed Other Columns")
in
    #"Removed Duplicates"

So no need to loop through anything again.

Thank you for your response and hint. The limiting externality is the amount of files and resulting response time.
Folder.Files() would be nice, but each file-server contains millions of files in constantly changing directories.

Table.Combine(Folder.Files("\\server01\???"),  Folder.Files("\\server02\???"), more...) requires hours to answer.

The (common?) SME use case is a dynamic, multiple folder-select starting from different main directories.

Loop: For fast response, the user selects folders level by level. Easier approach highly appreciated
Step1: User-select of server(s)    & call Folder.Contents( "get only (next) 1st level directories for selection" )
Step2: User-select of 1st.folders & call Folder.Contents( "get only (next) 2nd level directories for selection" )
Step3: User-select of 2st.folders & call Folder.Contents( "get only (next) 3rd level directories for selection" )
stop if no further user select, else continue loop until last deepest level

more PQ-conformant approach would be great help

Regards

Hopefully pointing to a working solution: to be further generalized by recursive call, i.e. flexible folder-levels.

Idea: Each User-Folder-Select returns parent/child folders, which is like browsing the windows explorer (standard)
(Pretty sure, there is a conformant & better standard off-the-shelf solution, but ignored or over looked here)

// fct named GetSubDirs (apology if too trivial, mimics only one step of explorer browsing)
= (MainDir as text) as table =>
    let
        // GetSubDirs queries (for each row in a table) MainDir only the next level SubDirs 
        Source = Folder.Contents(MainDir),
        SubDir = Table.SelectColumns(Table.SelectRows(Source, each ([Attributes][Directory] = true)),{"Folder Path", "Name"}) 
    in
        SubDir

calls custom-fct (probably be better & faster done as if nested)

let 
    // Sub2Dirs (table[column] with Sub2Dirs) gets for each row get all next level Sub3Dirs
    Sub2Dir = Table.TransformColumnTypes(Table.SelectColumns(Excel.CurrentWorkbook(){[Name = "Sub2Dirs"]}[Content], {"Sub2Folder"}),{{"Sub2Folder", type text}}),
    CustFct = Table.TransformColumnTypes(Table.ExpandTableColumn(Table.AddColumn(Sub2Dir, "SubDir", each GetSubDirs([Sub2Folder]), type text), "SubDir", {"Name"}, {"Sub3Dir"}),{{"Sub3Dir", type text}}),
    Result = Table.SelectColumns(Table.SelectRows(Table.AddColumn(CustFct, "Sub3Folder", each Text.Combine({[Sub2Folder], [Sub3Dir]}, ""), type text), each ([Sub3Folder] <> "")), "Sub3Folder")
in
   Result

possible value relevance: Most companies are SMEs (future value/cashflow). Most SMEs are not fully digitalized.
Many SMEs are MS-clients, still running file-servers, many run RDBs, fewer RDFs or kafka, i.e. data is stored in files.

The wish is to have a stackable select-ETL (until full digitalization, if at all) to select/access file-data via PBI (PQ/PP).

AIM: Enable any user to browse & combi-select multiple subdirectories to query file-content with separate ETLs.

Regards