Oh, I missed that when testing out "prone" and "go prone". Both just seemed to make you go prone, but it makes sense that one is actually "toggle prone". Thanks! I will try it out again.
I guess there's nothing to do but jump in and test everything out. Which will take a while, as there is no way to know when the controls are valid, that is, which are just for infantry, and which work only when you're in a vehicle/aircraft etc. You can figure it out most of the time from the name of the control, but not always.