blackpill Vanadium is based on upstream Chromium, so if the removal of a feature is not mentioned in the release notes for Vanadium, I think it's likely that Chromium removed it (for whatever reason). I can't find a feature with that name in the tab overview of Vanadium. But I see that it's possible to select all tabs, then unselect the tab you don't want to close, then select to close the selected tabs. Sounds like that does the same (but with slightly more taps)? In the tab overview, select the three-dot menu > Select tabs > Select all tabs > unselect the tab you want to keep > select Close tabs.