I just open the project and delete anything that’s not part of the song I want on itself and do a backup to a new folder (with ‘minimize audio’ etc. ticked). The arranger track is very handy for defining different songs.
Same procedure over and over. I end up with the ‘big’ project untouched plus a folder for each song which really just contains the files belonging to the song.
Good idea to do a backup before, it’s possible to create a mess and lose stuff.