Flaperon question

Hello all, I have used Inav as well as Mission Planner, however I am new to Qgroundcontrol. I cant see anywhere in the plane setup how to configure flaperons. In fact the setup only gives me the option of one channel for ailerons. Can anybody help?

Rudy, you have to do this in the mixer file (PX4)

Where would I find info on how to use the mixer file for flaperons? thanks

Rudy, it took me also some time to understand the mixer. But its worthwhile to dive into.
The starting point is here:
I started to use the profile Maja Bormatec in QGC. Then I put my mixer on the external SD card.
attached is one of mine:AAERTWF.main.mix.pdf (23.3 KB)