[DaveBlake]

I can't figure out if it's possible to make a node like this. I'd like one that shows only songs an artist's featured on, with none of their own songs. 

Currently no, but it is something that the underlying database and schema is more than capable of doing. So I would recommend tagging accurately (not trying to trick Kodi into it with bespoke tag values), and then talking to me on the thread on the music support subforum about extending smart playlist and custom node features in the future.

I am already aware that users would like to be able to show just album artists (excluding the featured/guest artists) but still optionally see the other albums that these artists feature on. Something that is currently tied into one setting. Seeing just the featured songs is closely related.