After installing the add-on, there's an eye-icon on the top right of the browser, which opens a popup where the stats and config are displayed.
There is (likely) already something like this out there, but I still wanted to build it for fun.
If interested, the source code can be found on GitHub: https://github.com/Tch1b0/doomscroll-blocker
A little more insight into my motivation: When bored or procrastinating, I often open YouTube just to watch a video or two. That then often spirals into around an hour of watching random YouTube videos, resulting in me being completely mentally drained when closing it again.
For myself this add-on has helped a lot, because now when the "video blocked" screen pops up, I exit that YouTube-binge-trance-state and become aware of how I was just about to waste my time and energy.