Curious, what display/screen size are you mostly using?
I find TST quite hard to use on a Macbook / Laptop screen... it's much better on a bigger screen though, and best when using a second/separate display/window for it.
When only using the MacBook, I make use of ctrl-uparrow to switch between browser and VSCode. I have tree style tabs in the Firefox sidebar, not a separate window.
To be clear maybe the term « awful » was a bit harsh, I don’t want to shit on TST/Sidebery, I know the limitations they face on Firefox. I said it multiple times, but I’m mad that seeing the relative success of TST/Sidebery in their add on catalog, Mozilla didn’t invest anything in experience around vertical tabs, and tabs in general. Arc is fundamentally a big rethinking of what tabs should/could be in a browser.
Last year I've used Sideberry extensively. It has some nifty features that TST does not have.
Do these two extensions look native to their host OS? Nope. I can live with that if don't need to use another closed source Chrome clone.