I wish, but it isn't. There was a request a few years ago for tree style tabs to be implemented in Vivaldi, but I think the dev didn't like the conflict with th

I wish, but it isn't. There was a request a few years ago for tree style tabs to be implemented in Vivaldi, but I think the dev didn't like the conflict with their own tab layout implementation. Seems to me there's a subset of power users on Firefox just waiting for any other browser to implement tree style tabs.