OVERVIEW
After a Collection is created, you can edit it (including managing Sub-Events) from the Event Summary screen.
EDIT COLLECTION DETAILS
Open the Event Summary screen for the Collection.
Click pencil icon.
Edit the Collection details as necessary.
Click Save & Close.
EDIT COLLECTION DETAILS FROM CALENDAR VIEW
Open the Calendar View.
Locate the Sub-Event that belongs to the Collection.
Click on the context menu icon.
Select Edit option from the Collection section.