Currently, we have a nice system in place where if you have a Viewbox that already has a child, and you attempt to drag in another Element to it from the Add Element Panel, a red tooltip will appear stating "[Element] cannot be added to [Viewbox], it can only have one child."

However, this protective and informative system doesn't extend to Element Duplication in the Navigator Panel, and makes it appear as if the Duplicate function in non-functional.

Repro Steps:

1) Create a Studio Page featuring a MainPage.xaml

2) Introduce a Viewbox Element to the RootGrid.

3) Introduce a TextBlock into the Viewbox.

4) Right-click on the TextBlock, and from the 'Edit' section of its context menu, observe how 'Duplicate' is an enabled action.

5) Select 'Duplicate'

Observe how no Element duplication occurs.

Expected Results: Attempting to duplicate a second child Element within a Viewbox (or any other single-child Element) displays a Toast notification reading "[Element] cannot be added to [Viewbox], it can only have one child."

Expected Results: The 'Duplicate' context menu option under the 'Edit' category is greyed-out/disabled when a Duplication can't be performed in the specific context.