I'm logged into office/excel 365. Why do I have to login again to get access to addins?
fix the above
The addin now supports single sign on. If you are logged in Excel, you won’t need to sign in the addin again. This requires you to be on latest monthly build of Excel.
Amit Oberoi commented
Thank you for your feedback. We are already working on implementing Single Sign On and hoping to enable it soon. Once SSO is in place and you are signed in with your work/school account, you'll automatically be signed in to the add-in. Personal accounts (hotmail.com, outlook.com etc.) are not supported, you can continue in unsigned mode to limited use of add-in.
You can see our public roadmap here - https://www.microsoft.com/en-us/microsoft-365/roadmap?filters=&searchterms=visio