This article goes over some things you can do with Dual Operator mode on the M300
To enter dual operator mode on the M300, you must first bind controller A, then bind controller B. Once both controllers are bound, you assign the function by selecting the icon on the screen.
In the below example, the controllers have been configured so RC-A has full control of the aircraft:
The options to take photos/videos are not on the screen, which tells us that we can control the aircraft
RC-B has full control of the gimbal and options for photos/videos are available. The drone icon is white so the RC does not have control of the aircraft.
So RC-A controls only the movements of the drone. RC-B controls only the gimbal. This function can be useful for a variety of situations where the pilot must only focus on flying. Other configurations can be set by selecting which RC has control over what based on the icons.
More information about dual operator mode can be found on page 51 in the M300 Manual: https://dl.djicdn.com/downloads/matrice-300/20230518UM/M300_RTK_User_Manual_EN_v4.0.pdf