Harmony Tool Question

Is there a tool that allows the next frame to automatically become a copy of the previous frame? I am wondering this because even though I can see previous layers and know where to draw, I might want to keep part of the object in place. ex) someone stretching an arm (I don’t want to redraw the body every frame. I was thinking about the duplicate frame option, but that wouldn’t be automatic and I would have to do that for every cell. Or maybe I am thinking about this wrong. Any advice would be appreciated