Hang in there - it is possible! Snap a photo of the rig... I'd like to see it.
Are you, by any chance, trying to make a TailSitter VTOL? Sure looks like it....
Motor mixes are connected to Stabilized roll?
Servos mixed to pitch?
Yeah... you're at the same point I've been all winter with my project -frustrating TOTALLY! One of the guys in my club who is EE (etheli - see link below) has contributed to the betaflight code reminded me that INAV, BetaFlight are open source and are not "commercial plug n' play" because basically it is a bunch of guys putting the code together for fun. I applaud them for there efforts, but it is not plug n' play if you do something other than stuff that has been tested.
I'm sure you've seen this:
Setup for a Fixed Wing Aircraft
Boris' Note:
I would not trust this as nobody is testing it, but it may work.
iNav fork puts a lot of effort in airplane modes. Its better to try them.
The page is to help those that wish to Experiment and Test Fixed Wing functionality with BetaFlight.
Do Remember that YOU are the TESTER.
And do remember that I am new at this too, so I don't KNOW the answer... just try telling you what I'd do...
I've just got a micro F4 board to work on the wing, one motor, but I wasn't adding any new stuff,
So it sounds like you need to remap what would be PWM 5 to the UART Tx pin.
This resource for Serial_TX 1 has to be turned off, which it is with "resource SERIAL_TX 1 none"
Now that SERIAL_TX 1 output pin needs to be fed a resource.
I'm assuming you want servo 5 to operate the retracts?
From the lines above, resource B05 is going to a servo plug (which would have been labeled PWM5 on a full-sized F4)
I don't think this matter but you don't want two resources connected to the same resource so I would disable that output with
"resource SERVO 5 none"
From above it looks like you are wanted servo 5 to be operated with resource B05.
Map the B05 resource to the Serial Tx 1 pin:
"resource SERIAL_TX 1 B05"
Let me know what happens... I'm trying to do kind of the same thing on Micro F4 Omnibus only I'm just goofing off trying to map a servo to the motor 2 pin since I only have one motor and to the Serial_TX 1 (just to see if I can).
I really hope that works.