I just tried to post on this topic (May, 2023) so I apologize if this duplicates my post.
I am using a 1Tb micro SD card because I have thousands of tracks and playlists. I use M3u files for my playlists. There are thousands of curated playlists in my collection.
It is no longer feasible for me to scroll through the Playlist listings, so I started using the 'Folders Hierarchy' feature. I'm sorting my artist sets into subfolders of various Genre folders.
Now if I have 10 album folders by an artist I can just scroll to the appropriate Genre and easily find the artist. I was hoping I would see the playlists in those folders. Alas.
Please make it possible for me to see the m3u files in those folders.