change my sprite during the work (reuse it)

can I change my multi sprite during the work on the game? for example I created a big multi sprite of my player by using TexturePacker. I import it into unity slice it and create an basic animation of my player.

after sometime I decided to add another animation to the player, the original sliced multi sprite have a lot of empty space inside, the question is there any way to reuse this multi sprite without slice and create animation again. I know that I can import new multi sprite with all the images together slice them create new animations and switch them in the animator controllers but I look for easier way to not touch my old images, just add the new one to the multi sprite. when I import by TexturePacker I so that I have .txt file with son can it help me? there is a way to do it with unity?

thanks.