Configuring Addition Actions for Edit Offer

I have a requirement to add an additional action to the When and Why section of the Edit Job Offer page, but I can't figure out where this is configured. I've tried Experience Design Studio, Page Composer, and Configure Actions, all with no luck. I'm fairly certain that the X - Central HR Use Only is a custom action, so I'm pretty sure this is configurable and that I'm forgetting something silly. Any suggestions folks can give are appreciated! Thank you!