Build in response to Report on where Reports are being sent - Report Lab - The Orion Platform - THWACK (solarwinds.com).
Frist block in report shows only scheduled reports (email, save, or print).
Second block shows all reports that are not scheduled (in any way).
Unfortunately, the actual email addresses are stored in JSON text, so there's no way to "report" on it. If people used good names for the Actions, then you might have the information you'll need.
No custom properties are used (or displayed)