Thanks for the thoughtful review! I agree with you that UIs can be both featureful and quick/easy to use, and that's what I set out to build with Tab Stash. I'm glad you're enjoying it!

Regarding your feature request, Tab Stash now supports Firefox multi-tab selection as of version 2.3. You can Shift-click and Ctrl+click tabs in the Firefox tab bar, click on any "stash" button (in the toolbar or stash list) and Tab Stash will save only those tabs you have selected.

I'm aware of the issue with dark themes, and unfortunately as far as I can tell, there is no reliable way for extensions to detect a dark theme, nor does Firefox give extensions the ability to specify dark/light icons for address bar and sidebar icons like we can for toolbar icons. But I'll keep an eye on this to see if it changes in future Firefox releases.