Sketchup 2016 .stl plugins?

Yes it can, I just had to sign out to check, the free web version will insert .stl.

On another note, you don’t specifically say you are working one handed, but as SU is quite 2 handed it’s handy to know that you can use an onscreen keyboard as your second hand when needed. I posted a little gif about it here.

Copying Bezier Curves With Only One Hand Working

SketchUp