My favourite vertical tab extension is Vertical Tab Reloaded, but their scrollbar cover half of the close button. Then I tried Tree Style Tab, which fixed my issue with VTR but it has a tree which I don't like.

I have searched for nice middle ground but Sidebery is more than just middle ground. Super easy to customize. I can have usable vertical tab that don't use tree system.

If there is one thing I missed from other extension is, TST's ability to search and filter tabs. Which is an additional addon that you have to install in TST.

Also color customization is kinda confusing. I can't figure out how to change certain part by matching what it's said on the settings. The color of suspended tab are too dark, trying out to change settings one by one doesn't seem to fix it.