Not exactly following what you're trying to do, but you can setup a new part and add custom properties to that part, you can link those custom properties, then save it as your part template.
You mentioned plate and cut list. Are you working with weldments, and is the description property you mentioned being driven by the weldments profile sketch (.sldlfp file)?
I have custom properties that link to my bom and drawings setup and my part template.
What I am trying to get at is to be able to use the bounding box as my stock size. I have the parts as weldments to enable the bounding box option in the cut list. I can get the size of the block but it is not linked to the properties. Also by doing it this way I can get it to show up in the bom, just as an indented bom, I would like to try to get a way around this. Is there possibly another way to create a bounding box for stock size without using the weldment feature?
I am not using profile sketches for the weldments.
I am unable to edit anything in this box. I want to be able to change these references and save that as a template