Not currently possible, but is a known requirement http://jthink.net:8081/browse/SONGKONG-299 and is in my Critical list, meaning that it is high priority and I aim to do it soon.
I would love to see this also, with maybe the possibility to move featuring artist back to the song and not to the artist field. Ever since musicbrainz went to ngs and moved the ft artist to the artist field, it has really messed up my tagging.
Yeah, that would be ideal. But I'd take any solution.