Alright, so from my experiments, it looks like there is NO WAY to just say “right now, play an animation at this point in the graph on these bones” without erasing whatever custom animation was playing before, even if it was in a different slot and different bones. You can only have one custom animation playing at any given time. (By “custom” I mean callable as a one-time play from a function, aka a punch or reload animation.) The only ones that can play at the same time on different bones are the looping unchangable anims that are based on player state (such as walk, run, etc.).
I hope I’m wrong about this, because it seems like a serious handicap. Does anybody else have a solution? (I’ve tried using both montages and sequences, they both have the same result, playing one erases the previous montage/sequence.)
EDIT: Just noticed “Multiple Montage Support” in the roadmap. So it’s definitely not there yet, but it looks like it’s coming