In order to use IQNOX widgets in a mashup you will need to set the TemplateStore property on the mashup itself. In the Explorer tab, select the mashup and search for the TemplateStore property. If you don't already have a TemplateStore you can easily create a new one by creating a new Thing and using the IQNOX_Widget_Template_Store_TT Thing Template or you can duplicate an existing TemplateStore.
All IQNOX widget styles are stored in templates. All these templates are stored in a TemplateStore thing. You can have multiple TemplateStore things for a single application, and you can change between them at runtime by binding the TemplateStore property on the mashup/master. This means that you can change all the application styles based on user preferences or actions. For example, creating a Light and Dark mode for your app.