There's a nice new site called https://daily.dev, but they keep bugging me to install a browser extension. The idea a website needs access to somewhere I make financial transactions is horrifying.
If you haven't tried it yet, both Firefox and Chrome offer different profiles[1][2], which comes with separate cookie stores and different installed extensions. The Firefox ones have a "this one goes to 11" level stupid UX (it's about:profiles, then click on Launch in New Profile) but to make up for it they offer Containers[3] which regrettably shares the same extensions as the host browser but awesomely hard sequesters the cookie and localStorage from other containers, and from the non-container default. Many people use it for all things QA since it's painless to log in to a website (AWS, Azure, etc) using totally different credentials
The DailyDev plugin only has access to "https://*.daily.dev/" and "https://*.dailynow.co/". It is also not required, you can just go to app.daily.dev yourself (I did not want to install the addon on my main PC)
1: https://support.mozilla.org/en-US/kb/profile-manager-create-...
2: https://support.google.com/chrome/answer/2364824
3: https://addons.mozilla.org/en-US/firefox/addon/multi-account...