In order to define an additional tab globally for each product page, navigate to Theme Settings -> Single product -> Tabs and define a new tab in the appropriate field.
Sorry, but there’s currently no way to add a secondary additional tab via product metaboxes, it requires customization and this is out of our Theme Support scope. We appreciate you taking the time to let us know what you’re looking for most of the improvements we make come from ideas and suggestions like yours, so thank you, and have a good day!