I have an API Management instance running where users can login using only Azure AD. There is a single Administrators account, but it is using the legacy User/Password Identity. I cannot remove the user. I want to assign a user from the Azure AD to the Administrators group, but I can not figure out how.
I have followed these steps by Microsoft but they just seem to redirect me to the legacy portal (or the new Developer portal if I change the URL normally) with my default Administrators account logged in.
As far as I know, we can't add another user into "Administrators" group.
The document you provided is used to login another user(which is not admin) as administrator. So the result page shows your default administrators account. The title "How do I add a user to the Administrators group?" of the document is not very accurate.