Multiplex Profi Tx Manual page 16

Apart from the standard curves the Profi gives you the option to create
a bespoke curve if you require, here's one made up to mix rudder
control into nose wheel steering
In the mixer definition menu (ABC1) a new mixer called Wheel+ was created,
which was assigned to the nose leg servo channel in the servo assignment
menu (JKL4), an input from the rudder was added to use curve 1
In the mixer menu (GHI3) opening the Wheel+ mixer and rudder input
opens the seven point curve, scrolling down to each position P1 thru P7
allows you to specify the mix input at each position.
Profi – Mixers
3 - Servoside Mixers