I have added 2 new viewing access levels:
*) Non-voting access
*) Voting access
in addition to the default Public, Registered and Special.
In the CB Plugin Manager, if I edit a plugin (e.g. Forum Integration) and select access level "Non-voting access", when I return the CB Plugin Management tab, the access is displayed as "Voting access". If I choose "Voting access", the access is displayed as "" (empty).
I have not yet tested which access level is actually enforced.