Ah it seems that there is this program called keynav. Something I guess I could have guessed.
For browsers I love to use these pentadactyl/vimium/... extensions. Would there be anything similar for reguar desktop applications. I get that it would be a huge effort to support all the different toolkits though.
https://beta.docs.qmk.fm/using-qmk/advanced-keycodes/feature...
It doesn't require any special support and works in every OS.
Here is how it looks in ZSA visual configuratior, for example: https://configure.ergodox-ez.com/moonlander/layouts/ZrQev/Eo...
One advantage you get with this method is that you can e.g. bind a key that sets the grid size and position to match the active window, which you obviously can't do in keyboard firmware (example: https://lesderid.net/keynavish-demo.webm).