Appointments that have been cancelled or even past appointments (and entries) can be easily deleted from the Samsung calendar.

Android 10 (One UI 2.0)
Step 1:  Open the  Calendar -App
Step 2:  Tap on the  Day
Step 3:  Tap on the desired  Event
Step 4:  Tap on  Delete
Step 5:  Confirm with  Delete
  1. Open the Calendar-App
  2. Tap on the Day
  3. Tap on the desired Event
  4. Tap on Delete
  5. Confirm with Delete

Samsung Instructions