Linked item icon - external and internal links
 

I am finding that the same icon appears if I import an item linked externally, typically a web address (which will not therefore have stored data in it) as when I clone (copy) an intem internally (when there usually will be stored data within UR).

For me it would be tremendously useful to know when data is not in fact held internally in UR. Although I can see this for an individual item, I can't find a way to look at the data explorer pane and see, looking at the tree and a string of items and their icons, which of those items is in fact not stored internally.

Am I missing something obvious?

The item icon does not indicate that information (the shortcut overlay is used to indicate logically linked items). You can show the Document Size column in Search Results/Child Items to see that information for multiple items. We'll consider adding a stored indicator in the item icon for a future release.