Fixed size of tab thumbnails
I keep my tab bar on the right hand side, so I have vertical tabs, and as soon as there are more than maybe 20 tabs, no thumbnail is visible. Even below that amount, thumbnails get very narrow and hard to see. Using the default top tab bar position, tabs thumbnails get very narrow too.
I think we should be able to set the size of the tab thumbnails and have it kept at that size no matter how many tabs are open. Or at least, thumbnails should get a fixed size, assuring that they remain visible even with a lot of tabs. This implies that not all tabs would be visible all the time, so tabs would be scrolled like on a carousel.
I also would like to have this feature! Like Showcase extension for Firefox has: https://addons.mozilla.org/en-US/firefox/addon/showcase/
It adds a scrollbar if you have too much tabs open. Here is a screenshot but without the scrollbar: