Well, if nothing else, I may provide some comic relief.
The car is not here right now, so I don't have the owner's manual in hand, but if memory serves, the button is ESP (electronic stability program) and it has only two settings: on and off. I remember reading in the (400+ page) owner's manual that even turning the setting off does not stop the system from braking a spinning tire, not necessarily in response to yaw. I obviously need to learn more about this .... I'll check the MB racing forum, there are actually a few guys who drag these beasts.