Issuing Gimbal Reset Pos command

I’ve poured through the docs and couldn’t find anything obvious. Mission Planner has the ability to issue a “Reset Position” command which causes the gimbal to return to a “neutral position” (centered on mount in both pitch and yaw).

I’d love to be able to hit a button on my controller to the same end, but cant find the option (or script) to do this. Any pointers would be greatly appreciated.

Autopilot: Cube Orange
ArduCopter: v4.4.4
GCS: (tried both Mission Planner and HereLink QGC)
Mount/Gimbal: Siyi A8 over DroneCAN, linked to MNT1 setup using this guide.

Can provide additional details as needed.