Adding this feature would allow the user to place a marker at the current vehicle(or camera) position. These markers could be either short markers or tall markers that could be seen in the distance like a single pole in a scenario. The markers would be implemented with a keyboard shortcut, and the markers could possibly be numbered to differentiate the different markers. The short markers could be used to show how far a car jumped or where it crashed. The tall markers could be used to find locations in the distance on maps or can be used to mark where the AI is not working so that multiple AI issues can be fixed at once. I think this feature would be useful for several situations and not too hard to implement (I'm guessing)
the closest there is now is maybe the path which is drawn after you use script ai manager to make a route for a vehicle, though its a line and not a marker