Thank you for writing.
I managed to reproduce the described behavior. We will consider making the hidden items show at design-time in one of the next releases. For the time being if you want to do some additional settings on a hidden/collapsed menu item, you can select it from the drop down in your Visual Studio's Property window. The other way to achieve your requirement is to set the Visibility at runtime, but not at design-time.
I have updated your Telerik points for bringing this issue to our attention. Do not hesitate to contact me again if you have any additional questions.
the Telerik team
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