You can use the data fields for anything you’d like to put in there and have them placed on the Store Pages output with the proper field codes.
A custom fields extension add-on has been on the list for some time. The original iteration was flawed and dropped in favor of a database extension system built into the main plugin. It is what drives all of the * Extender products. As soon as I can get caught up on support and customization tasks and get my new hires on board I hope to get a new “Extend This” add-on pack launched.
Probably a couple of months out unless I get a long boring weekend with no other obligations to craft this on a whim.