A few options:
A) Create a custom property, of type String, on your valve (and matching property on the popup window to pass it to) that has the tag path to the more complete UDT tag you are looking to use in the popup window. You can then pass this property to your popup window. From there you can use this tag path string in an Indirect Tag binding on a another custom property in the popup window that has the same data type as your complex UDT. (there is probably a better way to pass the name of the tag to the popup window)
B) If your Simple UDT has a similar name to your complex UDT, you can pass the TagPath property of your simple UDT to the popup window. You can then use the name in an indirect binding that you modify to match the name of your complex UDT (similar to option A)
C) Pass the parameters to the window via scripting, instead of the GUI interface. This will allow you to modify tag names and how you pass parameters as you see fit. How exactly depends on your UDT naming/setup.
I’m sure there are many other ways to do this but these were what I could think of off the top of my head.