When I apply display:none, how would I get back the element without using the browser console? If I change things from the console, does your tool watch the changes via mutation observer or does it only know about the changes from the visual tool itself?

It only knows about changes from the tool. I started this project by attempting to listen to changes from DevTools via a Mutation Observer but it was extremely noisy on many sites.

I haven't added display and visibility yet, it's on the list, but you would simply toggle them back. There is an element selector sidebar so they're not going anywhere.