You'll have to explore all the various custom settings in the Fly app available for each of the programmable RC Pro buttons and combination button settings, and choose where you want those features among the options available for each button and button combination.
However, there is no ability to simply toggle the Auxiliary LED ON and OFF and back to ON. Instead, it is always a
3 way toggle cycle from the default of AUTO to ON to OFF and then back to AUTO. If you turn it ON and turn it OFF and then
try to turn it back ON, nothing will happen because it is now back to AUTO. You'll need toggle it twice to go from OFF back to ON.
It's a potential gotcha, because you have to turn it ON to be able to turn it OFF, and get it out of AUTO, so you don't nightblind yourself as you are hand-catching after dark! If you failed to turn it ON, after trying to do so, after first turning it OFF, you may think it is now still OFF, but it is back in AUTO, ready to night-blind you!
Toggling also only works
after the motors are armed. You can no longer bench test the functionality without first arming the motors. I had a return set up with my
Mavic 3 last January, as the app at that time did not state that it only worked in flight, like it does now, and on the
M2P, you can bench test it easily, so I expected it would be the same on the
Mavic 3! Not so! Fortunately, I independently discovered the motor arming requirement before returning it, as DJI didn't know about it either at that time, and neither did anyone else, including the dealer!