Differential Thrust with Pixhawk 6c and PX4

Hi,

My son and I are building a Horten flying wing, and we currently have Elevon and differential thrust for yaw set up with the RC.
However, we would now like to add a Pixhawk 6c, mostly for the stabilized flying mode, as the plane can be a handful to fly.
As far as I am aware, differential thrust is currently not possible to set up in QGroundControl, but it is requested, maybe only for VTOL? (Control Allocation: Differential thrust vs control surfaces, servo failsafe mode by sfuhrer · Pull Request #23245 · PX4/PX4-Autopilot · GitHub)
Is it possible by other means, e.g. the mixer files - if so, is there a way to upload the mixer file with QGroundControl, and also, is there a documentation for it (I searched, but did not find a good doc file for it)? Or is the only way to keep having the remote control do the differential thrust, meaning the yaw cannot be stabilized by PX4?

Thanks,

Raoul