Timeline Knightlab Viewer to Display Caption or Credit of Media

I’m hoping to display an element/value from the media metadata attached to an item on the knightlab/timeline module on Omeka S. The option to change the item description is there, but no options are available for fields from the media to get displayed. Here’s an example page. George Mackey’s media has a description of Quips & Cranks, 1911, pg. 28.

I’d love to get media caption and/or credit to display. I played around in the Knightlab documentation on JSON (as that’s what goes in the viewer options in the module, right?). I also poked around in the module files and was unable to get any values assigned to the media to display. If dc:description for the media isn’t preferred, I’m happy to use another element.

Thanks for any insight!