I have a template which utilizes a UDT as its main parameter. On clicking the template it opens the control popup passing it the same UDT that it references:
The control template then refernces the components that make up the UDT (in this image showing one of the control buttons that is setup as a bidrectional property binding to the UDT component ".manual")
The objects on the control template read the value of the UDT components fine, but do not write down to them.