Looks nice! I have a few questions after watching the video in the readme if you don't mind:

In sidebery my pinned tabs are always at the top, but it looked like the pinned tabs in yours are part of the scrolling area? One thing I like a about pinned tabs always being visible is being able to see when I have new email/slack/calendar notifications even if scrolled way down the tab list. Is that possible with yours?

I usually have 500-1000 tabs, have you tested for any potential usability bugs when having way more tabs than fit vertically on one screen?