Can not add invitees to a calendar event after the event has been created I can not find a way to add an invitee after the event has been created and the invite emails sent. Is it possible?

Below is the already created event, where I do not see the field to "add invitees" any more:



Here is an event that has not yet been created, thus possible to add invitees:



EDIT: I use Exchange as the backend for the calendar... though had same issues with Google Calendar as backend as well.

Using Calendar Version 9.0 (2155.15)
If you click on the list of invitees, there should be an "Add Invitees" field which appears below the list.