You could pass as CommandParameter the "MenuItemsSource" of the Menu and inside the command to find the desired MenuItem whose visibility you like to change. The IsVisible property is bound to the Visibility property of the RadMenuItem and changing its value will change the Visibility as well.
We have modified your sample with the described above approach - please, notice how the visibility of a specific item changes when the Button that is added to project gets pressed.
We hope this will help you.
Telerik by Progress
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