Thanks Marc. Your solution works perfectly. Cosmetically I would like it if the pane scrollbars could be the modern 3D ones used on the modern tree, but that's fairly minor cosmetics, and I understand that panes are properly system objects.
While we're on the subject of trees, I've specified "5 columns" with the system property, but the actual display has many more. You can see by the image I attached the right pane shows all 5 columns, but the horizontal scrollbar indicates there is that much again off to the right. I don't want the user to be able to scroll to those blank columns.
Any ideas? And yes, although I've been using LabVIEW for about 15 years, I'm new to LV 8.