Introduce a 'deliberately not here' list

[singaround]

Although the song list is comprehensive, there are some songs that are deliberately not there. They might be because we've decided they're impossible to make appropriate, or for some other reason.

Sometimes it can be hard to know if a song is just "not in the songbook yet" or has been carefully considered and found worth of retirement or rewriting

Take John Kanaka, it's not there, but John the Slacker is... How would people discover this?

I'm wondering about section at the bottom of the list for 'songs we don't normally sing' or similar, with a bit of info on why, and links to the appropriate replacements (if extant)