I wish we had a simple UI we could bring up to expose cookies to other tabs (arbitrarily). I just want a list of cookies with rows marked in green if they're being sent with requests, red rows for cookies that would normally be sent for the same [sub]domain but are currently not, and then gray cookies that are established from completely unrelated domains. To me this would be better than maintaining tab profiles/containers that are for business/personal/etc. This would be like a one-off UI before you determine if you want to establish a container profile.
Also I want them to take tree tabs seriously. There is a plugin for this, but it doesn't look like a tree at all.. I am grateful for the plugin, I just wish it were a UI effort focused on. I cannot maintain more than 40 tabs open and easily browse through them. I'm tired of the response being "well don't".