A competitive advantage for Brave (since Google now prevents the plugin that prevented this happening from working) is to create a setting that prevents all tabs from inadvertently being closed. Nothing is more infuriating when scrolling up and inadvertently going too far and clicking the “X” in the upper right corner. Sadly, there are some research sites that make user scroll all the way up to the top in order to edit their search. Lost 15 tabs from inadvertently clicking .25" too high.
I would LOVE to see an UNDO opportunity when I accidentally close a tab. Sometimes, the fingers get ahead of the brain, so this would be a very useful feature that would lead the browser market.