How can i mix channels on my rc in mission planner?

I have a caterpillar rover, and a skydroid h12 pro remote.
One motor controller goes to each track, accordingly there are only two connections to the main outs on the pixhawk orange cube
I need to mix channels (pitch and throttle for example) so that one stick on the remote will spin two tracks at once, can I do this via Mission planner? I can’t find a channel mixing function on the remote control
I hope the context is clear, I’m writing the question through a translator).

If you are using Mission Planner, you are probably working with ArduPilot. This is the PX4 forums. Please raise your issue in