There is "rudder_trim_limit = 0 ; Rudder trim max deflection angle (absolute value) (DEGREES)"
No idea if it actually works.
Well, I do ... It doesn't work.
That is: tested in FSX-Accel.
I can't test it in any P3D version myself, but I highly doubt if it would work in P3D.
In FSX-Accel, I added
rudder_trim_limit = 30
in the [airplane_geometry] section of a few aircraft.cfg files.
But the result of reading (A:RUDDER TRIM,degrees) always results in a value between -10 and +10 max.
For whatever value of rudder_trim_limit = ...
And, as I expected, the same goes for adding aileron_trim_limit = ... to the aircraft.cfg: (A:AILERON TRIM,degrees) is always between -10 and + 10.
Hence my conclusion in post#2: it's fixed, and cannot be configured.
Again, I tested this in FSX-Accel, but I would be highly surprised if this feature is actually implemented differently in P3D.
Would be curious to know in which document you read "rudder_trim_limit = 0 ; Rudder trim max deflection angle (absolute value) (DEGREES)"
But even if you did, I'm still betting it won;t work in P3D.
Untill proven otherwise, of course ....
Rob