When attempting to share the vApp, no group tab shows up for a user with the Catalog Author role.
Cloud Director 10.6.0.1
The Catalog Author Role does not have the View Users and Groups permission in Cloud Director 10.6.x
If desired, add the View Users and Groups permission to the Catalog Author, or create a cloned Role and add the View Users and Groups permission to the cloned role. Assign that role to the desired users.