Last time I tried Vivaldi, the vertical tabs were not 'tree style'. By that, I mean they were all listed directly underneath each other rather than indented to show from where they were open.
Do they indent like this? This is a really important aspect of tree style tabs because it adds another dimension of information. It also means that I can just minimise that tree of HN tabs down when I'm looking at something else.
It's my one complaint about Vivaldi's implementation, yep: you can "stack" tabs, but this creates an absurdly tiny target space to click between tabs, and there's no way to create tab trees instead. It would be lovely to be able to create them, because I often create trees of tabs when browsing sites like HN: I pop tabs open behind HN as I see interesting links, and then click down the tree to go through the sites themselves.
Take my current Hacker News browsing: https://imgur.com/a/p3w77RJ
Do they indent like this? This is a really important aspect of tree style tabs because it adds another dimension of information. It also means that I can just minimise that tree of HN tabs down when I'm looking at something else.