[Zubersoft]

Unfortunately, the batch edit functionality is not smart enough to allow you to add new data without impacting the existing data for a song. You either have to set all of the songs to the same values for a given field, or you can mark that field as not being changed. Currently, you can long press songs, tap the three dots at the top right and then add them to collections or setlists. I'm going to expand this to allow them to be added to any field in the future. Another thing I can consider in the future is having some kind of toggle for the batch edit where you can either edit existing metadata (the current behavior), or just add new metadata (which could get a little weird if you try to add something that already exists for one or more of the songs). 

For now, I would recommend either using the option to add songs to existing collections, or you can go to the collection tab, edit the collection and add the songs in the group editor.

Mike