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