I am active in a handful of sites like superuser and stack overflow. When I find time to come here, I often work on several questions or answers.
I was always annoyed that I can log out all my communities at once, but cannot log in the same way. Today I found by chance why there is no instruction to set this up: Because it should happen automatically. (Why am I requested to log in again before I can post a question even though I have logged in)
And, once you login to any Stack Exchange community, you are automatically logged in to all the communities that you have ever joined — in that browser session.
Now that sounds so good; I want that too please.
I am working on different computers like a sys-admin, mainly using Firefox but also Chrome and MS Edge or whatever browser I find where I need to work. Never has my login worked automagically accross Stack Exchance sites. It might not be a browser problem.
I am always logging in to each site by the same e-mail address and the same pw. I believe all those "accounts" are together, because I have something like a "combined inbox" for messages and the same user-photo is showing in the top-bars.
Where can I look up the configuration for this please? Normally I allow cookies for each session and only have them swiped when I close a browser.