I'm a Business Unit Manager and I cannot edit any of the asset groups in my business unit.
The Edit button next to each asset group in the business unit is grayed out.
The asset groups were created by the Manager of your QualysGuard subscription and assigned to your business unit.
The Manager of your QualysGuard subscription will create the business unit and add various asset groups to it. As a Business Unit Manager, you will have access to these assets, but you will not be able to edit any of the Manager-created asset groups.
You can create your own asset groups from the assets contained in the Manager-created asset groups. The asset groups can be identical to the Manager created ones.
Qualys Support KnowledgeBase