open shortcut (automatic)
 

could "open shortcut" work directly when item is selected in the Data explorer, without having to go and point at URL attribute? In the more advanced version, user could choose which attribute would be default for "open shortcut" command.

That's an excellent idea. Even if you have the Open Shortcut icon on a toolbar, it doesn't become active until you click on the URL attribute, making it pretty pointless.

Ctrl+J (Item | Open Document). Item | Open Shortcut is intended for opening a URL at the current selection (current attribute, URL in detail pane, etc.).

Also, if 'Tools | Options | Miscellaneous | Launch favorite externally with Ctrl down' is checked, you can use Ctrl+Alt+Shift+ or Ctrl+Alt+ to externally launch a favorite's URL via the favorite's shortcut key combination.

yes, but it would still be nice if user can open some kind of default URL of an item. I have a library and the documents are on local disk, if I want to open the relevant pdf, it's a bit clumsy as it is at the moment ...