Brief description of the outcomes that you expect from this feature:
Possibly with opacity change it could enable you to select Sketches and 3d Model that is at 100% in opacity. Basically opacity change is a soft hide feature.
What can’t you achieve without this feature?
With opacity set lower, it will help you visualize, instead a hard toggle on and off.
If this is to difficult to implement, a great shortcut would be a way to “Pick Face Color” (incl transparency). Is so, you could pick of present item or even build a small selection on-the-side to use.
When using the “Show Hidden Edges” feature you can see that curved pieces (in the corners of this piece) are invisible and hard to make out.
However, when you highlight the object to select pieces, you get a much better visualization of your object through the opacity. I can easily make out the curved edges behind walls. So the visualization is there, just giving users the ability to manually adjust this would be very welcome.
[I can only post one embedded media image as a new user so my reply to this will be the highlighted visual]