Rated 3 out of 5 stars
Please add tree management and auto-hide and it would be a major hit!
Side Tabs is meant to be simplistic. I plan to include auto-hiding as well as the ability to customize the appearance, however I have no plans to sort tabs into trees or groups.
If tree style tab management is what you want, stick with Tree Style Tab.
Or maybe try Vertical Tabs which offers tab grouping: