it would be great if pinned tabs can also have thumbnail on hover

I've been using this with all the tab preview features turned off (simpler, faster, no distractions) and it's simply superb. With the tweak to hide the default top tab bar, this completely feels native in terms of speed and responsiveness. Thanks for creating and maintaining this wonderful extension. This made me use firefox again as my default browser :)

Wish the vertical tabs can be positioned to the RIGHT side of screen.

Sure it is better then default. In year 2020 one row for tabs :D Oh browsers are trash. My father use average 30-50 tabs. It is very good old Firefox works ok, with this new no thanks. I need browsers for computers we are using now 8 GB is average... I have 2x 8GB - 4 slots. I use 6 groups with 200 tabs without any problems... I can backup groups with Tab Group and use it anywhere.

I really hope that will soon any new groups of developers created browser like it was old Firefox, but I think we will stuck with this "new" Browsers and they are the same as IE in windows 95. They can`t even added by default Last Closed Tabs icon.

Go job for addon. Maybe I will use it when Firefox v52-57 will not work anymore on pages, but before that All-In-One Sidebar is the best sidebar in Browser History and Tab Utilities Fixed etc. for fast and easy browsing. Yes "Tab Scope" is awesome I use it now and for a lot a lot of years. Awesome addon preview with zoom scale by right click. Old days when Firefox was created for users...

Chrome: 68.91%
Firefox 9.25%
Desktop web browser market share according to StatCounter for October 2019.

In last 10 years Multi-row by default in all browsers not in year 2020 only one row same as 40 years ago :D :D. In settings user will set min/max size. Who even use 10" screen any more PC users use average 24" (20"- 28") on this screen who even care, if they are 3 or more Tab Rows. Every user use Browser different...

Congratulations! Quite as good as Vivaldi's thumbnails of tabs. Please add grouping tabs function :)