Ignition 8.x Vision -
I have a popup window with a UDT as a custom property. Everything working as it should in client, but I haven't been able to figure out how to get it to link while in the designer. With other custom properties you can just change the value of the property manually to view in designer but I don't see how to do this with the UDT property.
As far as I can tell, there is not a way to directly edit values inside a UDT from the Property Editor. One workaround is to create additional custom properties and link them to the members of the UDT custom property. This allows you to edit the UDT members from the designer.
One of the many reasons why I dont' use UDT type parameters 
@Micah_Gross I believe he's talking about actually linking the UDT type parameter to a UDT instance for testing the graphics with it. When I first started using Ignition years ago, I remember fighting trying to work out how to do it and gave up. Then I realised the other limitations of using them, and gave them up altogether.
Conversely, Perspective's props.dropConfig is very useful, and provides the functionality of the Vision UDT type parameters, only without its drawbacks. Instead of binding the props to a specific type, the Perspective version just copies stuff to specific parameters, e.g. copies the tagPath of the dragged tag/udtinstance into the view param you specify
