The key thing would be some sort of input-buffering system, where you can have lots of things bound to keys, and the framework will actually buffer things. Generally web browsers and modern UIs in general throw away input on reloads and such, on the generally-correct but very novice-biased theory that you didn't mean to be inputting into a screen you can't see yet. If you undo that and allow buffering keystrokes across loading actions you could start recovering some of that expert-level speed, where you can be using screens that aren't even loaded yet.
"Expert-focused" UIs don't have to be bound to the terminal. That was all an accidental thing.
Expert-focused UIs are nearly dead because all our UI frameworks actively block them. That is also not a fundamental fact of computing and can be undone.