

Indeed. It uses some of the vertical tabs features in Firefox, but adds workspaces (~tabbed tab window) that you can assign default containers (like banking, personal, shopping) to. Tab groups are missing, but are being worked on. Don’t expect nested tabs or trees like Sideberry or TST offer though. Honest disclosure: the implementation is not fully polished yet. The location where new tabs are opened or their remembered location after closing/opening the browser is not consistent.
That popup you mention sounds like the zen web panel rather than the sidebar. In total that gives 3 concepts: vertical tabs, a floating web panel next to that and the sidebar. I like what they’re trying to do, but it’s not all polished yet with some odd UI glitches or things requiring (re)configuring like the toolbar. That combined with bad font rendering and missing tab groups made me switch back to FF for now…where I now disabled all usage data sharing options.