Very useful. In case it's helpful to anyone, I've made a diagram for my own layout.
This is different from the layout I use for Lix. Obviously, the biggest difference is that in NL I don't have any hotkeys assigned to specific skills; I don't find it worthwhile to learn a skill layout for both games. In NL I use the "previous skill" and "next skill" keys, as on original Mac Lemmings. (In fact, I was the main advocate of these keys being included in NL, so I'm very glad they have stayed in!)