To cancel a trip, you will need to mark the entire trip as Inactive. A change status module will then appear and a custom cancellation reason can then be selected.
This will automatically set all flight legs within the trip to cancelled and remove the trip from the schedule.
CREATE CUSTOM CANCELLATION REASONS
To create and manage cancellation reasons, access Operations > Operation Settings > Cancellation Reasons
Inactive trips are still accessible by going to Trips on the main navigation, select inactive to true and click search. Make sure to have the correct departure date set or uncheck the departure date filter.