Hello Kevin,

I would like to note that this item has already been addressed. Feel free to upgrade in order to benefit from the fix. 

As to the workaround, in order to remove the database restrictions, it is necessary to uncheck the "Allow Nulls" field in the respective table in the SQL server. You can create a custom EditAppointmentDialog and override its ValidateInput method where you can validate the data in the respective controls on the form. The following help article demonstrates how to replace the default edit dialog with a custom one: https://docs.telerik.com/devtools/winforms/scheduler/dialogs/editappointmentdialog