When I open Workbench the first time, I get the "Pick Prod/Dev, Pick API version, agree to license" screen, with a "Login with Salesforce" button. When I choose Login, if I have an active session (or sessions) already in the browser, Workbench will pick the most recently started session. If I want to login elsewhere, I have to logout. But it has grabbed my active session - logging out will log me out of all of my other browser tabs in the same org.
Here's a common scenario: I need to do something in two sandboxes (say, dev and uat) using Workbench. Sometimes it's comparing some data, sometimes it's exporting from one and importing to another. Nothing I couldn't do in another tool, but Workbench is easy and convenient. So I'm logged into dev and uat sandboxes, and I launch Workbench. It auto-attaches to my uat session. I export some records, and now I need a Workbench session in my dev org. Opening it in a fresh window and choosing Login will just attach to uat again. Choosing log out will log me out of all active UAT windows in the current session (and there may be several). How can I get Workbench to show me the login window without ending my other session?
I've considered using a second browser, or using an a "private browsing" tab, but I'm hoping there's a built-in way to get Workbench to start a new, clean session.