Thank you for the brain dump. I liked that this came up. I used tree style tabs for a few years starting way back in maybe 2012, but eventually just abandoned it because of the same performance problems you mentioned. I didn't replace it with anything good, and was just recently getting annoyed at the state of things as i suddenly find myself context switching a lot on mini projects. I was just setting myself up in Emacs org mode and felt i needed better integration with the browser. I have a little extra time to put into making it right. I think at the very least i am going to write some small amount of integration for the currently clocked Emacs org task, the main OS views, and Firefox, just Mac OS X to start, all open source.

Anyway, i was exploring options and i was glad to find your experience. I think i am ultimately looking for something similar to what you want and maybe will email you at some point to ask about this if i do indeed get a little deeper into it if you don't mind.