Allow song and set-list specific notes
It would be very useful to me and my band to be able to add notes to songs, e.g. about arrangement. This could be done on the set-list level (maybe additionally on the song level, too?). Or to make this even more flexible: Some sort of key-value annotations? I can think about some usecases like tempo, songbook numbers, etc.
Those notes can be displayed in smaller / different font along the song text.