[woodslanding]

I can certainly imagine a situation in which a setlist might contain songs from multiple collections, but in practice I'm not sure I've ever done this.  And if it ever happened more than once, I'd add the song to the new collection.

When opening a setlist for editing, it would be nice if the collection was remembered, and didn't have to be reselected.  Also, when importing from the setlist page, it would be nice if the collection was autopopulated along with the setlist.