Since this thread is almost 2 years old, I'm only responding for others who may cross it looking for an answer to this issue.
Now, I'm not sure if this is a feature exclusive to HTC phones because I have the Droid Incredible, but I was able to create a navigation shortcut on my phone's home screen/desktop. One tap on the icon and I'm on my way, with the gps already activated of coarse.
All I had to do is long-press an unused space on the home screen, select "shortcut" and select "directions & navigation". A pop-up will appear requesting the destination address, mode of transportation and a name for the shortcut. You can also pick one of seven icons. Enter the info and name it HOME and you're done.
Some apps like Folder Organizer have the ability to create a shortcut in a similar manor but give you dozens of icons to pick from.
Hope this helps.