I’m not sure if this will be a solution, but you can access that property directly by typing it in your script. That “Choose Property” dialog won’t let you select it directly, since it detects it as a folder, but that doesn’t prevent you from using it in your script.
(The same thing is true if you’re selecting a component v.s. selecting a component property. You can’t select the component itself in the “Choose Property” dialog box, but if you type the component path, you can use that component object in your script.)
The part I’m not sure will work is whether you’ll be successful passing that UDT into the other window. If you type the property path directly, and it doesn’t work because of the object type, you may need to switch your templates to use the UDT Path (as a String parameter) instead of a direct UDT parameter.