Christina Miller I was trying to do the exact same thing as you when I found your post. I’m just shocked ESRI doesn’t provide these kinds of reports out of the box.
I spent many hours trying to figure out how to read the webmapID in a given app/dashboard with Python (which I could see in AGOL Assistant JSON view). Luckily, I eventually found the solution: See line In :
Attached is the script I developed. It searches your ArcGIS Online for any web apps and dashboards and will then list each of those items and its details, the webmap associated to it and its details, and then every layer in that map and it's URL.