Being an Administrator and being part of the Administrator rights group only affects whether you can log in with the Administrator tool. It does not give you any additional capabilities within the client UI and does not circumvent workspace visibility.
As an administrator, you can use the administrator tool to adjust membership of workspaces and therefore can add yourself to workspaces to gain visibility.
Note:
For further information about this please see the FAQ item "How do I add a user to a workspace if I am not a member of the workspace?" to be able to add yourself to workspaces that you are not a member of