Hi! Thanks
Not sure it’s possible to completely “remove” the original assets, as they are used at run-time by UE4. I would have suggested the “assign skeleton” action too, but clearly it’s sub-optimal. UE4 reference bones by name, this is the reason it makes the “union” of them (it keeps the old ones to be able to use the old animations and add the “Mixamo” ones to be able to use the Mixamo animations).
Maybe others have some tips to share.