Hi xizetatamias,
I just wanted to follow up to check if the resolution we provided for adding classes in QuickBooks Online (QBO) has been helpful for you. As mentioned, users with the appropriate permissions can add, edit, or delete classes. If they are designated as Primary or Company Admin or a standard all-access permissions, they should have the ability to add a class.
Check out this article to learn more about user types and permissions in QBO: User roles and access rights in QuickBooks Online. It will help us understand what role we should give based on their work.
Please let us know if everything is now working as expected or if you're still experiencing any problems. We'll be glad to assist further if needed.