There are two ways to cancel an appointment. Go to the time slot of the appointment in the Scheduler.
Click on the edge of the time slot. This will open up a side menu having the Cancel appointment icon, highlighted in Image 1. Click on it.
Click on the time slot to open the Schedule information screen. From the Canceled By box at the bottom of the screen, select Patient/provider/Clinic. Click on button. This cancels the appointment, leaving the designated time slot vacant.