Jellyfin has full playlist support. AFAIK it keeps the playlists themselves as text files on the Jellyfin server that just reference the media files themselves,

Jellyfin has full playlist support. AFAIK it keeps the playlists themselves as text files on the Jellyfin server that just reference the media files themselves, wherever they may be. Adding playlists to your Jellyfin server does not seem to add files onto your NAS, in my experience. That's just the default behavior, though. Could be that you could set it up to save the files to a folder in the NAS.