This is not a problem for all operational attributes (most likely dependent on the user modification flag in the attribute type).
The attribute in question is one I just added to the schema and as far as I know it is not actually operational. I cannot add a value of that type to an extensibleObject entry.
The attributeType is definately in the schema (I can see it in the cn=schema entry and I can add a value of that type to an entry using another LDAP editor app) .
I think this bug is more to do with LDAP Studio not reading in the schema for some reason. I have also tried reconnecting by the way.