GREAT WORK ! i had like 100 subtool, and i was trying to fix the overlap in meshes for 3d printing in parts. This saved me like a week or even more of work ! maybe there is a tool for this, but i didnt do the researchs anyway, lol. maybe latter
I just want to say 3 thing in my opinion would make it even better.
- layers menu - colors or some division betwen layers - that would make it easy to the eye to identified each leyer
- List of command - delete “hide selected and shows others” (its more easy just click on the eye icon) making a shorter and efficient menu
- Change the name of “Show selected, hide others” for “Show only” or something more shorter and easily to read (maybe im lazy, but saving that time every time you use those tools, make a workflow faster, and it takes just a little effort to do change that name, so, am i the lazy one?
those things would make a workflow much better 
in a 1 to 10 scale. 9,99 its not 10. 10 its perfect. though 9,99 had an error however small it may seem - Someone, somewhere, sometime.
omg sry 4 ma englis :v
thanks for this !
Cheers!