Animation system in UE4 is really great. Sadly, but anim editors are awful. Just tried to add some additive layers to imitate punches from Idle anim. It’s just impossible: no snapping to frames, no autokey on changed values, selection of multiple keys not works so on. You’ll better remove this functionality before it can be used or make tools more user-friendly.
The same goes to Pose Asset Editor - the worst editor ever created. Did you actually give it to try to animator before ship? Try to change existing pose, you’ll be surprised, but this just can not be done! you’ll have to create new pose from tweaked one, delete old pose and then rename new one to old name.
As for Montage - it’s pure madness. I don’t even will start typing all its issues, it’s just broken and should not be used unless you want go crazy.