Here's a common situation for me: I often rename an mp3 file or re-arrange the folder structure, which breaks my playlists, since the playlist would be referencing an invalid file.
For example, I have a file called "U2 - One.mp3" in multiple playlists. I decide to rename it to "U2 - Achtung Baby - One.mp3" which breaks all the playlists that it belongs to.
What are good ways to handle this scenario? Here is my solution, but I welcome any other suggestions. I would create custom ID3 tags for each playlist, like PLAYLIST_A = true. PLAYLIST_B = true. PLAYLIST_C = true. That way, when I change file name, I can simply filter using my custom ID3 tag, then quickly recreate the playlist without losing the file.