Ashley I can appreciate your point, but in this case you can simply make the behavior work as you intended - on a negative acceleration (deceleration) with time scale and zero gravity, it should not start moving in the opposite direction when reaching 0 speed. It should stop to a halt and stop being active until timescale kills it. It is currently adding gravity and there is no advantage of having it go in the opposite direction
So no need to add a new gui element- simply fix the behavior's bug.
then we will have the feature and at the cost of no extra input box