Thank you for your patience and helpfulness with this. Greatly appreciated!
Couldn't I just activate the URL Downloader Repository:
So that when I want to add a file that is URL resource, it's available as a choice in the File Picker? (Or will that URL resource module repository whatzit only accept "external" URLs such as youtube.com, dropbox.com, et al?)
That way, when I click "add resource/file", I could double-click into a folder through that interface. Then I could "upload" a URL that points to a file in another course in Moodle, and it would be listed in that folder.
Currently running version 2.1.1, build 20110801.