I've been trying to figure this out for a couple days now but can't find anything about it in the manual.
Any track can be a Return track (provided it is to the right of a track that will be sent). You configure the sends for a track by tapping the track header. Audio to 2 and 3 are the tracks sends. You could make a new track, rename it C, and then track C will come up as an available send in the other tracks routing options.
Alternatively, you can use the Audio output module (under Util/Misc) to set up sends within your rack. This would give you optionally more than just two sends per track.
Very cool, thanks for clearing that up! I was hoping it would've been possible to just add "Audio to 4" or more sends though. Hopefully this is added in the future.