Looks like that's not available yet. Will check back with this beta later when that's available. Going back to the "classic" viewer.
Hey Alan Rea,
You can see the ArcGIS Online Map Viewer Beta Roadmap here:
Map Viewer Beta Roadmap
Looks like adding a URL will be coming Fall 2020.
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You can also add a layer to the map using the URL parameter for now
Thanks Russell, but I'm not seeing where to enter this URL parameter. The Add Layer dialog seems to only allow entry of a search term. Where can you put in this URL parameter?
You can add it to the end of your dashboard url:
Here is my dashboard url (It's set to private so it won't be accessible by you but you can see the url):
At the end of the url you can add another parameter with an ampersand so the above example would look like so with the new part in bold:
Retrieving data ...