I’m happy to leverage some functionality that would avoid the need to modify the core code, but I would prefer if the plugin itself supported the quantity field natively. I know there are some styling and documentation concerns, but the implementation itself seems relatively straightforward. As written, if the max_quantity is missing or is one, then the plugin is completely backward compatible since the field itself is not rendered.
I’ll clarify that the above code works as is, but needs to following:
* The inline style on the additional select box is not ideal. Feel free to give it a proper class name, and put the styling in the CSS.
* Additions to the short-code documentation are obviously missing.
