Unfortunately this does not cover my use cases.

You see, I am allowed to have "hidden" meetings during my work time. In my organisation all calendars are shared to everyone (helps in finding suitable times for internal meetings etc.). However, all of my meetings can't be seen by everyone (some of our clients require this), yet my collegues need to see that I am reserved. Hence the need for "private" appointments: people can see that I am reserved but do not see why. This is how my organisation works.