Hello, Jim,     

Thank you for sharing your feedback with us. We will consider it when implementing this feature.

However, you can also have in mind to setup different access for the users you want to restrict. The following articles may be quite useful for this case:
https://docs.microsoft.com/en-us/windows/security/identity-protection/access-control/access-control
https://docs.microsoft.com/en-us/windows/win32/fileio/file-security-and-access-rights

I hope this information helps.

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik

Hello, James, 

The current implementation of the file dialogs is intended to show the context menu with the default options similar to the Windows File Explorer. There isn't appropriate public API to plug into this logic and control what options to be displayed in the menu or prevent the dialog from opening. However, it seems to be a reasonable request for exposing such API.

I have logged it in our feedback portal by making this thread public. You can track its progress, subscribe for status changes and add your comments on the following link - feedback item.

I have also updated your Telerik points.

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik