Hi Michael, first let me say thanks for your interrest in this Open Source initiative.
I think your idea with multi value categories is usefull and I am thinking about implementing it in the next release.
The other requests are currently not possible due to the Lotus Notes Security. The secret information is not just beeing hidden from displaying, it is encrypted with the public key of all users in the list. Therefore you can't use a group. This is high secure, even registering a user with the same name does not give access to the information.
Maybe it is possible to add a function to reduce security by just using Reader Fields, those can contain the name of a group too, but keep in mind, Information is not encrypted with Reader Fields! If you have access to the servers filesystem you can read all information!