Using QDesigner Plugin

[wysota]

Then why does my application (using a custom plugin in the Designer) need the plugin's DLL at runtime? The application has been linked against the plugin's static lib -- I thought it would prevent the need of the DLL at runtime, the DLL would be used only by the Designer.

I don't know what you linked against but if the plugin is required then it means your application is missing the code of the widget in question.