Should all Signals admin account changes will be handled by our Informatics Support team?
Who should add new users?
Tenant owner is first and main admin, and Informatics Support should be asked for assistance if you need to change _ownership_ of the tenant(license), replace old owner with new one.
But there could be more admins in Signals, and adding/revoking Signals Admin rights can be done by anyone with corresponding user permissions.
You can learn more about user management in Signals -> User Menu -> System configuration -> User Menu -> System configuration guide -> User roles.
Adding new users should be done by Tenant Owner, who is admin by default, or one of assigned Admins, not by Informatics Support.