Could you elaborate, please? (link, pointers?)

Opening new incognito tabs/windows will let you log on with different accounts in each window.

No, cookies are shared across incognito windows (try gmail.com)

Ah, didn't realize that. Thinking about it, I've only used this 'hack' to have two different gmail accounts open at the same time (one in normal, one in incognito).

No we can't. Please don't suggest to go incognito.

There' a user switcher button in the top right corner, you can have multiple browser sessions with seperate histories / cookies (e.g. work / personal)

Holy moley! I never noticed that!