First you need to create an molding alias that is going to be assigned to the CLOSETROD PART

Create a profile for the new molding material

Then we need to create a Closet Rod Part who will have the previously created material assigned to it in all molding material schedules

Now we need to assign the material to the part in the material schedule

To add the closet Rod to a cabinet you need to create a new molding at the cabinet level then select the Closet Rod Length material previously created.

By selecting a molding material you will see that the molding profile is greyed out so you dont have to select a profile.