I switched to Firefox away from Chrome recently. I am happy with this but I wish they had a friendly UI you could bring up to expose cookies to be shared between tabs on an opt-in basis. Cookies should be isolated per-tab by default. Cookies and other persistent data should be forgotten as soon as the tab is closed. I don't like container tabs, I think it gets confusing to manage tab groups by profile. I want to quickly mouse over and say "expose this tab's cookies to this other tab".
I'm still sad I can't get perfect "tree tabs" going. I have a plugin I use to show parent and child tabs in a tree arrangement but nothing looks sexy about it:
https://addons.mozilla.org/en-US/firefox/addon/tree-tabs/?sr...
I want an actual tree of lines shown to each row/tab to quickly visualize how the tabs were created from parent-to-child. How it currently looks is too busy with borders everywhere. It's functional but not what I envisioned. I can't hide the tab bar at the top as far as I know. I'm just frustrated that I remember trying to make this work in like 2002 and it's soon to be 2019. I feel like browsers aren't made for workstations, but casual consumption. They should enable so much productivity.
I also wish they focused on minimizing and isolating references to various Web APIs, so it would be easier to unreference and orphan them - unreachable from advertisers.
(Unrelated rant?)