I noticed a little folder icon had appeared just recently and that if I clicked it, it... listed all the tabs, so I guess that was the list all tabs button. I actually rather liked it but hadn't yet trained myself in to the habit of using it. I hadn't even noticed it's now gone, but curiously it seems like for me it hasn't really gone, so much as it's become a down arrow icon rather than a folder. Sounds like this change is to make it optional, meaning it will otherwise stay there which tracks with my experience, but why has it become a down arrow now?