I've wanted to pursue them but my hope was to find software to do stateful/modal transitions. As a fake example, instead of pressing Alt+Z you'd press Alt then Z. It becomes a lot like modal editors, which is my favorite style of editing - i add a lot of usermode stuff into Kakoune to avoid key combinations.

So far i've not felt i could get software to do the modal editing i speak of reliably in all of my environments. I'm on NixOS right now, and i didn't want to manage the software. It definitely is interesting though!