I doubt it will be possible to add ONE plugin that does this, since there are so many versions of a nanoscale MOSFET, not just "
the nano-MOSFET". It's absolutely possible to use the Builder today to set up such systems, although that's not to say it can be a bit hard without guidance. So, I would not expect a plugin to solve the task, but rather a sequence of the existing operations - also known as a tutorial
It would help if people suggest concrete systems, though, since otherwise we'd just be guessing, and there is a huge difference in building a MoS2 thin layer, an Esaki diode, and a Si nanowire MOSFET.
So, please post systems, pictures, ideas, etc, and we'll assist via tutorials, videos, etc, as best we can.