Combining drawing layers

I’ve seen from earlier posts that this isn’t possible due to exposures etc. However it would definitely help my workflow (which granted may be a bit unorthodox). I think the exposure sheet issue shouldn’t really make it impossible, especially if you guys solved it non-destructively. So if you’re combining:

Layer 1: 1 2 3 4
Layer 2: 1 3 3 1

You simply go:
Layer 1: 1 2 3 4
+
Layer 2: 1 3 3 1

Layer 3: 1 2 3 4

Right? And you could provide the option “Keep current layers?” Maybe I’m missing something that goes on under the hood, but if you create new drawings on a new layer it should work, and it would keep me from copy/pasting 100 drawings and spending hours doing mindless work.

Here’s the post I was referring to.

Thanks –

[edited to include link]