> The best two examples of this are the Arc browser and Chrome OS. But I think Arc is actually the more interesting of the two experiments. Their first innovation was to break the idea of tabs at the top and instead move it to be a sidebar model.

I will forever hate Arc for popularizing vertical tabs the way they did.

Vertical tabs were a thing since at least the Tree Style Tabs extension (2007), except the Tree Style Tabs were infinitely cooler, because they were a tree, not a list, and right click->open in new tab, would open the new tab as a child of the current tab.

So you could have a hacker news tab during your break, start opening a bunch of articles, read through them, simply un-expand the HN sub-tree, go to work, and then re-expand it during your next break.

Because of Arc, everyone is now implementing vertical tabs, but no one is implementing Tree Style Tabs, and, probably no one ever will again.