The following error occurs when closing Property Builder at design time:
Hi, chaoyuan,
Thank you for reporting this. You can still add/remove a page using the options from the smart tag or do this programmatically as well: https://www.telerik.com/products/winforms/documentation/controls/navigationview/hierarchy-support#building-hierarchy-with-nested-pages-programmatically
Regards,
Nadya | Tech Support Engineer
Progress Telerik