Here is how to change the settings if you don't want notifications to be set by default when you create an event.
1. Open the app's settings screen and tap "Settings".
2. Tap "Reminder settings" at the top.
3. Open "Normal event reminder" and "All-day event reminder" one at a time, and on each screen, tap all the checkmarks so that none are selected.
After this, notifications will no longer be set by default for new events.
When you do want a notification, you can set one while creating the event.
Thank you.