I find myself going back to the home screen naturally rather than going for the ALT TAB. Then if I click the desktop app shortcut tile it takes me back to the desktop and launches a new window/instance. It seems like this is already the perfect UI to simply take what once was task bar tabs and put them as tiles. Then I could see the current state of my desktop app in the tile, and clicking the tile would restore it to the focus. Not sure why they went half assed, keeping ALT-TAB and leaving the desktop apps out of the tiles interface, rather than just allowing me to full screen a desktop app as a tile.
Thus I am wondering if there is something I can do to the short cut tile to make it go to a running desktop app rather than just being used for launching anew.