AUX control ftom mavros, without pertubing the multicopter itself


I would like to send a Actuator command to activate a magnetic gripper from Mavros, without sending the Pitch, yaw, roll. There is a group_mix enum in the Mavlink message (as well as in Mavros) but it looks not implemented in the PX4 Firmware.

Mavros message :

PX4 Firmware implementation

What is the correct way to do control AUX channels?