Sending a specific command

I’m working with QGroundControl and a Pixhawk. I have created a gimbal manager class using c/c++.
Fortunately I have successfully managed to connect the three using Mavlink-router. Now the gimbal manager class can read attitude from Pixhawk and send a heartbeat to QGroundControl.

Now my task is to see if I can receive a command from QGroundControl to change the attitude. The command is GIMBAL_MANAGER_SET_PITCHYAW I guess.

I’m wondering if it is possible to get the command individually or do I have to create and start a mission , then configure other commands so that I can get to the command I want to test ?

Thanks for your time.