Telerik Visual Style Builder is not available at design-time because it is a large enterprise application rather than a simple tool that can be used within Visual Studio. Instead, you may create your own themes by starting a stand-alone instance of the builder and then import these new themes at Design-time by using our RadThemeManager.
More information about Visual Style Builder and how to create new themes and modify existing ones you may find by following this
I hope this information is useful. Do not hesitate to contact us if you have any other question.
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