I was struggling to copy a NavigateUrl from one External Template asp:Hyperlink. However it turns out the problem has already been addressed by the Sitefinity team!
Lets use the External News Template (ListPageMaster.ascx) as an example (which is what I was having problems with).
Okay, so see how the Hyperlink has an ID of "fullContent1"? ...well you can make up to SIX of those and the backend will automatically add the NavURL into each of them by itself...how cool is that.