The developers recently shared a blog post, detailing the feature. The browser already had Tab Stacks to help you stack multiple tabs in groups for easier management. Now, with the latest update, Vivaldi has added the ability to expand a stacked tab in a different tab-bar located right below the primary tab-bar.
Two Level Tab Stacks
Currently, when stacked tab-groups are expanded to view the included tabs, they open up on the same bar. With a secondary tab-bar at the bottom, users can now easily sub-categorize their primary tab-groups for easier management while browsing the web.
Now, although the secondary tab-bar does take up a small amount of extra screen real-estate on the screen, I do not think that will be much of an issue for users. On the flip side, with full-sized sub-category tabs at the bottom bar, users can instantly spot the tab they are looking for. Moreover, having a dedicated bar for the secondary tabs means users can manipulate and organize the tabs just like they do on the primary bar.
The Two-Level Tab Stacks will be turned on by default on the latest Vivaldi v3.6. However, you can turn it off and use the Compact Tab Stacks from the browser’s Tab Settings page. And the feature is currently only available on the Windows version. You can download Vivaldi for free from its official website.
