While I agree with the idea of separating hidden geometry and hidden objects introduced in SketchUp 2020, it is sometimes a tad annoying that my old shortcut doesn’t allow me to toggle both the way I’m used to.
This extension adds the menu entry View > Combined Hidden Entities that does just that. Just set up the shortcut of your choice and you are good to go. I’m using Ctrl+Shift+H.
I need more modifier keys. 
I use U and I for those. I use them even more often than Hidden Geometry so one key shortcuts are practical. I for Identical, U for being next to I and not already be used. 
Those are used for other things on my end.
I want to be able to add tongue position or foot pedals like those on an organ to get more combinations. 
I should make an extension for that…
Yes you should.
Joking apart, the idea of a dedicated keyboard for SU use would be interesting. I think you can get configurable keyboards (touch screens?) but I’ve not heard of anyone using them for SU.
