This extension will watch for anytime you visit a sentry domain. If you visit a production domain it'll note the org slug and copy the cookies you have into it's own local (nothing goes over the network) storage. Later, when you visit a development domain it'll see what org slug your using, and grab the cookies related to the org. So if you're logged into https://test-az.sentry.io you'll also be logged into https://test-az.dev.getsentry.net:7999 automatically!
This extension is open-source under the MIT license. Read the source code at https://github.com/getsentry/cookie-sync