We must make a distinction.
In Projeqtor, the chosen calendar is a tool to distinguish between which working days and non-working days are for each kind of resource group. So that you can plan as accurately as possible from the unavailability of each resource.
The agenda contains only the elements generated and specific of the tool Projeqtor , including of course meetings.
You can create a meeting, or an activity, and allocated resources on them, so this event will appear on the agenda of each resources. Other solution, you can create and name an administrative project. Then impute resources on it to indicate that they are unavailable (because they are present on an event wherever).
We have planned to impruve our agenda, now static, by being able to generate objects directly from this screen. Get in mind, this calendar is not and will not be like a traditional office tool, it is not its aim.