The PHP files in the zc_plugins/ebayintegration/v1.0.0/admin/includes/ebayeditors folder define editors which not only allow you to view and edit the attributes used to create an eBay listing, but also add data to the eBay API Add Item request to create the listing.
You can replace an existing editor or create a new one by adding a PHP file to the zc_plugins/ebayintegration/v1.0.0/admin/includes/ebayeditors/overrides folder.
There is an example editor in the overrides folder in the file autopay.php. It doesn't display or allow you to edit an attribute, but it does add an element to the XML used to make the request to eBay to add an item.