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I was exploring Chrome's tab groups feature, which is still in its experimental stages, and it's too basic, so I tried to find something better. Of all third-party extensions I've tried in my opinion Sidewise is nicest one. There is also Tabs Outliner, but I find it's very unforgiving as it's very easy to delete tabs and there's no way to get them back, where Sidewise has a built-in history of closed tabs, and many other nice features. I use both for different things, basically.

SideWise seems to work alright but when I wake a tab it creates a duplicate that appears somewhere else in the tree. This is obviously a compatibility problem with later Chrome versions. I wish the developer could look into this.