2 weeks in Hawaii scuba diving with my beautiful wife... ahh life is good.
now back to autocad... sigh.
Try this: Edit the Parametric Part, Create the symbol you want, then click on Modeling > Symbol and Annotation Plane > Design Blocks, right click and select "Add Schematic Block", select the plane you want and then select the symbol that you made.
Might not work, my head is still in Kona...
-Buzz