Go to chrome://extensions/shortcuts and set a shortcut on "Enter element zapper mode".
I set it to ctrl+shift+q because I kept accidentally closing my browser and I needed something to override it ...
I don't think that feature exists anywhere else and seems a trivial implementation of collaborative filtering to decide what to delete preemptively for each user.
The zapper will also try to detect and remove CSS rules which prevent the whole page from being scrolled.
For a general slide-in/pop-up blocker, try Kill It https://addons.mozilla.org/en-US/firefox/addon/kill-it/
isn't that just adding it as a ABP/ublock filter?
How this should really work is by maintaining two DOMs, one which the application sees, and one which the user sees.
Half baked is an understatement, but I guess it works sorta-ok for a half-day project. Pull requests are very welcome though!