Currently ran into a bug? on a SQL Managed Instance in Azure. On SSMS whenever we create a Login to associate with a user we dont see that login on the security tab on SSMS but do see the user on the database, is this by default in SQL Managed Instance? or is there a way to find an associated login to a database user, a view or dmv perhaps?
Please install SSMS 18.x, although is on preview it has a lot of fixes for Managed Instances. SSMS 18 has the best experience for Managed Instance users at this time.
Keep updating SSMS to get the best user experience with Azure SQL and Azure SQL Managed Instance.