TST Bookmarks Subpanel is an awesome solution to utilizing the mostly empty side panel in conjunction with Tree Style Tabs. This is the one light-mode add on that I think really fits where it sits. Not necessarily a necessity, but its convenience becomes present during normal use.

Excellent add-on. Would it be possible to add favicons and also the option to open in new tab (middle click) vs same tab (left click) ?

Add a pick-up of TST styles. Or own styles.

Piro, the great savior of Firefox.
Without TST, TST Hoverswitch (thanks to Klemens Scholhorn) and, now, TST Subpanel, Firefox would be unusable.
The 2-pane functionality would be a nice addition.
Excellent work and many thanks!

Since Firefox broke all my favorite extensions a year or two ago, I have been yearning to get back the split tab tree/Bookmark in one sidebar an older extension provided. At long last, it has returned.

Hi, thank you for your work. How about add 2 pane bookmark?

Thank you! It's been almost 2 years since I've been able to have my bookmarks visible at the same time as TST and finally Firefox feels whole again.