display only text files within parent folder and children

display-only-text-files.txt

Tree accepts only a few command line parameters:

c:\>Tree /?
Graphically displays the folder structure of a drive or path.

TREE [drive:][path] [/F] [/A]

   /F   Display the names of the files in each folder.
   /A   Use ASCII instead of extended characters.
None of the indicated parameters are a file mask or filter.

You can use dir with the proper switches, and redirect the output to a text file. You'll get the full path name to the files, but you can filter that out in later processing if need be with a for loop:

C:\>dir *.txt /s /b > filelist.txt

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It's actually not that hard to get your desired TREE output using FINDSTR regular expressions. :-)

tree /f /a | findstr /ri /c:"^[^| ]" /c:"^[| ]*[+\\]" /c:"\.txt$"