May I drop an idea for another feature?
Similar to the monitoring of music files in specified folders and auto-update of the music libraries (library settings), if such a monitored folder contains playlist files (e.g. m3u), MusicBee could trigger an auto-import of these playlists. That may not need to be a separate feature, but done in parallel to an update of the music library. A simple checkbox „include playlists“ in the library monitoring / update settings could allow for a switch to turn that function on or off as per a user’s preference.
I imagine this to be useful if external playlists are used (e.g. when MusicBee is used on multiple devices, which are supposed to use the same, synchronized playlists) and are modified more regularly.