While permissions can be set up for functions, the default behavior of vRealize Operations Manager is that every user with dashboard access has access to all dashboards. This is due to the fact that all dashboards are linked to the Everyone group.

To change the default dashboard assignment, go to Content -> Dashboards -> Actions -> Share Dashboards. Click the Everyone group and drag and drop all dashboards to the Operations User group. Next, click Everyone again, select all dashboards, and click the Stop Sharing button to remove all dashboards. The Everyone group should show zero dashboards assigned.

Those dashboards you would like to make available for your tenant users can be assigned now by dragging them from the Operations User group to the Tenant User group.