I am pasting the reply from the support ticket:
EditRecurrenceDialog is designed in such a way that can be called only from the EditAppointmentDialog, the reason is that the appointment should be in Edit Mode in order to be able to edit its RecurrenceRule. (that's why calling the EditRecurrenceRule command doesn't work in your case). So I am afraid that the needed scenario cannot be achieved - you should first open the EditAppointmentDialog.
We're sorry for the inconvenience.
the Telerik team
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