Is it possible to generate Sub-Layers?
No. How would you use it if it was possible?
Layers Panel might be what you are looking for:
Excellent! Thanks a lot!
But you should be aware that it is an un supported plugin.
Ok, what does that mean? It actually works fine.
The original author struggled endlessly with subtle bugs and finally gave up after concluding that they were due to limitations or errors in the SketchUp Ruby API. It works most of the time but occasionally fails badly.
I use it and have for some time. It does behave unexpectedly at times and it’s a shame the developer stopped supporting it. Still useful though. What a pity SU doesn’t build in some of its capabilities itself.