Creating a Widget Blueprint by right-clicking on the code class in the Content Browser is not a workflow that is supported in the Engine.
Depending on how a Blueprint is created from a custom User Widget code class, the resulting Blueprint may not be a Widget Blueprint as expected. Right-clicking on the code class in the Content Browser and selecting the option to create a Blueprint from the code class does not result in a Widget Blueprint, and there is no Designer tab available. However, using the Add New button to make a new Blueprint and picking the custom User Widget code class as the parent does result in a Widget Blueprint with a Designer tab.
The new Blueprint is not a Widget Blueprint, and does not contain a Designer tab.
The new Blueprint is a Widget Blueprint with a Designer tab.
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