Assign an event to a different calendar
1) Log in to Nextcloud and navigate to Nextcloud Calendar as described [here].
2) Navigate to an existing event as described here.
3) Open the event editor as described here.
4) Add an event to Nextcloud calendar.
Note that a calendar name appears in the upper left hand corner of the event editor. Click the arrow to the right of the calendar name. A dropdown appears which shows the calendars for which the user has write access, including calendars that are hidden.
Click on the name of the calendar to which you would like to assign the event. The calendar name in the upper left hand corner of the event editor changes to the name of the selected calendar.