Yes, it is possible to create new users in Apache NiFi with administrator privileges similar to the initial admin identity.
You can use the User Authentication Provider in NiFi to add new users with the desired level of access. You can configure the User Authentication Provider to use a variety of authentication mechanisms, including PKI certs, as you are currently using.
Once you have configured the User Authentication Provider, you can add new users and assign them to appropriate user groups with the necessary access policies. You can create a new user group with the same policies as the initial admin identity user group and assign new users to it.
To create a new user group with the same policies as the initial admin identity user group, you can export the policy for the initial admin identity user group, and then import it for the new user group. To do this, navigate to the Access Policies tab in the NiFi UI, select the initial admin identity user group, and click the "Export Policies" button. Then, create a new user group and click the "Import Policies" button to import the policies from the initial admin identity user group.
After creating the new user group and assigning the new users to it, they will have the same access as the initial admin identity user. However, keep in mind that granting administrator privileges to multiple users can pose a security risk. Make sure to regularly review and update access policies to maintain security.