Hi, cgs!
The ProiTX was called profi as it was meant to be for profis. Having taken over the mixer structures for the ROYAL and even expanding them (e. g. more parts!) almost all wishes a profi could think of have become possible.
The COCKPIT SX 12 however was not designed as a profi-TX so mixers are not as refined as in the ProfiTX. With the COCKPIT it is not possible to arrange mixers like with the ProfiTX. You have to work with the mixers as you find them there.
One advantage oft the COCKPIT-mixers is that you can save totally new setups in each flightphase - so you can run them as gobal mixers for alle flightphases in common or as local mixers separately in each flightphase.
So I am sorry for disappointing you: Mixers are not tranferable from the ProfiTX to the COCKPIT SX.
best regards
profimc
(by the way: I am user as you are - not member of the MPX-team!)