Stop point for Animations

I propose "stop points" when playing animations like you use when using a debugger in programming. It would be very useful to be able to easily create these stop points when clicking in the purple area. Left-Click is used to move the current frame pointer and can only be used in the purple area as well. Middle and Right-Click functionality also work in the rest of the area so one of those could be used to place the stop points. Maybe it is helpful to design the stop points in a way that they aren't confused with the Auto keying symbol. I thought about actual signs/Red Octagons but don't know if they are distinguishable enough at that size.