I have multiple accounts configured on the same yubikey, but it seems like any of the Microsoft login portals expect you to always use the account you most recently signed in with. So any time I need to switch accounts (which is often, I have different accounts for each different testing environment and access level), I have to type in my pin and touch my key twice - once to allow Microsoft to try logging in with the wrong account and fail, and then another time where it asks which account I want to use. 🙃