What are virtual tenants?
O365 Manager Plus' concept of virtual tenants is segmenting users based on domain, group membership, job location, and other user attributes for administrative requirements. Administrators can create virtual tenants pertaining to a specific department, team, project, and every possible user group, and delegate management operations on them to technicians.
Important points to consider
Before you begin, you need to remember that, once enabled, virtual tenant delegation cannot be disabled, and the option to delegate domains to technicians will no longer be available. In which case, admins have to create new virtual tenants with domains added to them, and delegate those virtual tenants instead of directly delegating the domains.
Refer the image below to know where to find the option to enable virtual tenant delegation.