Hello - by ‘a mesh within Rhino v7 that has entities on multiple layers’ do you mean that you have created several meshes and these are on various layers? As far as I can see stl keeps these as separate, at least on reimporting to Rhino. But as far as I recall, layers are not supported in stl.
That appears to the case, and I appreciate your prompt response.
Take for example an aileron on a wing. That moving surface is on a layer of its own, and so the wing as well. On .STL export/reimport to Rhino V2 as .stl, all the surfaces are welded together.
It appears there will be a need to create separate export files that showcase surface movement.