THEMA:

Yes, using the output mapping of the receiver via device manager works in that situation (thats what I mentionend in post 2).
But it is a kind of workaround, the main problem is the servo settings in the TX are logically connected to the channel number, not the function.
If after the primary setup you change the sequence of functions (eg "throttle, elevator, rudder" to "throttle, rudder, elevator") the servo settings are not moved to the new order, only the servo name is changed.

Right. That would be my wish for the next workaround, to no longer assign the servo settings to the channel, but to the function. This way, when changing the servo slot on the receiver, only the new slot would have to be set in the transmitter.