A Query About Rudder Mixing

In the wiki section on FBWA Mode, it says in part:

In FBWA mode the rudder is under both manual control, plus whatever rudder mixing for roll you have configured. Thus you can use the rudder for ground steering, and still have it used for automatically coordinating turns.

Does this refer to rudder mixing that is setup in the transmitter, or is it possible to setup rudder mixing within ArduPlane?

Yes! Take a loot at these parameters. There is also more information about how to tune them in the tuning guide.
https://ardupilot.org/plane/docs/parameters.html#yaw2srv-parameters

Thanks for that information @TunaLobster.

Since I can do the rudder mixing within ArduPlane, then I should not have any mixing in the radio transmitter - correct?

I assume that by “tuning guide” you mean the Roll, Pitch and Yaw Controller Tuning section?