I'm logged into office/excel 365. Why do I have to login again to get access to addins?
fix the above
We have started to work on enabling single sign on using the office 365 credentials for the addin. Once released, users will not have to sign in to the addin separately,
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