MM4 is no longer being developed!!!
Regularly back up your playlists to an "unwatched folder"- (not in File-Monitoring" by MM4
TOOLS > Scripts...Export All Playlists.

Please, please add a ctrl-z/Undo function. I just did it again - intended to delete a track from a playlist and instead deleted the whole playlist. It is unrecoverable - does not go to the system recycle bin. So very painful. This has been requested in the past, by me and others. Thank you.