I want to create a GSuite Add on for the Google Calendar where the user gets additional information during the creation process of an event.
For example: The user is in the creation process of an event and selects a specific resource for that event. (the event is not yet created). In the addon, there should be additional information about that ressource when the user selects this specific resource.
However the only there are only two triggers for the calendar add-on which are eventOpen and eventUpdate which both require and existing event.
So my question is how to interact between an Gsuite Calendar Add-on and an event in the creation phase.
Unfortunately, what you want cannot be achieved.
What you can do instead is to file a Feature Request by accessing this link here and provide all the necessary details.