I would like to be able to backup or copy JUST ONE collection from one tablet to another. I can't use the backup and restore, because the 2nd tablet belongs to another person and they have their own collections and set lists that I don't want to destroy.
You can do this by just sharing the songs, because collections are part of the standard metadata for songs. So open the collection on the collections tab, long press a song to start selection mode, tap the select all icon in the toolbar at the bottom right, then tap Share->Export as .msf. The other person can import this .msf file and it will create all the songs. As part of this, it should add the collections because those are part of the song metadata.
Mike