but listenback is not able to appear on the heaphones, is there a way to route listen back to different outs other than main?
or is it possible to have two talkback inputs?
No, I think the Listenback functionality is right now only routing automatic to the main speaker outs for situations like in separate "old-school" control room scenarios should appears.
RME should be thinking about modern "Home and Project" studio situations even in bigger rooms. Meaning one room situation for all. Yes, then you can speak together without any microphone to each other.
BUT: If each person (performer and engineer using both closed headphones for keeping back unwanted "Bleeding" signals. then it should be nice for the possibility in TotalFX to configure TWO Talkback signals instead of one Talkback and one Listenback signal in preferences. This means TWO Talkback microphones for the performer and the engineer. Both microphones are then still only working when the Talkback button is activated. And also the engineer can hear the conservation over headphones.