Hiya, I have recently been editing a skin (Well, what else would I be using the Skin Editor for? 
), and something that I often do is remove parts that I don’t want, and replace them ones I like from other skins. When I had finished working on the main part of my skin, I was then ready to proceed onto that second stage, so I added a new layer and typed in the IGN of the, ‘filler’, skin on the side, and popped it in. However, much to my disapproval, instead of adding the skin onto the currently selected layer, it just replaced the whole thing; undoing all of my work (I was also touching-up the skin; not just deleting parts :3)!
In case you haven’t worked it out already, my suggestion is that when you do what I did, the skin should just fill the selected layer instead of replacing the entirety of the skin; to avoid similar problems. Welp, that’s it, basically; have a great rest-of-the-day! 
P.S. I apologise if there is, in fact, some sort of, ‘Idea Submission’, section; I have simply missed it!