I have to create a group on one tab and then one by one put the other tabs on that group. Would be really easy to just click the left tab, shift+click the other end of the tab train that should become a group and right click on the selection to group them, or maybe close them or hibernate them (as requested here).
Ctrl + click for tabs with other tabs in between, too. I think Edge has that behavior. But, not Brave on Ubuntu.
Update: The functionality exists. I just can’t see that tabs that don’t have the focus are selected when using the GTK theme.