If you have an existing user who needs access to more content in Control Center, you can add them to another enterprise ID rather than creating another username for them to remember. After adding them, be sure to check their permissions. You can turn permissions on or off for whole sections or you can turn on and off individual permissions within a section. You can also make a user a system administrator so they can access everything for that enterprise ID.
Users can have different permissions for each enterprise ID they have access to. For example, you can be a user on three enterprise IDs and a system administrator on a fourth enterprise ID. Once you add a user to an enterprise ID, you can then manage the accounts and permissions they have access to as you do all other users.
Adding an existing user to another enterprise ID also eliminates the need to sign in and out using different usernames to manage multiple enterprise IDs. By adding a user to multiple enterprise IDs, they can toggle between them to more easily manage their portal tasks.