Unfortunately those replacements just don't cut it. They're too separate. Tree Style Tabs is irreplaceable for me.

Unfortunately these are tree style tabs in a separate window. Bad UX in my opinion.

Thanks for the suggestions, and last year I dedicated a six month trial to using those "separate-window" implementations in Chrome, but I'm very sorry to say they remained clumsy.

I group my work into topics by desktop; one browser instance per desktop, with an average total of 200+ tabs across eight windows. Restarting Firefox means sorting eight browser instances, one hotkey to snap them to half-width. Restarting Chrome required sorting sixteen browser windows, then manually aligning each primary window plus its tab window using the mouse. I tried, I really did, but that never became less of a pain.