I've never done it, and may be all wet, but I did a little experiment with one of Beersmith's Extract recipes.. (Muddy Pig Oatmeal Stout).
I first duplicated the recipe so I wouldn't destroy the original.
I then pulled up the Muddy Pig Oatmeal Stout copy (Extract) and clicked on the Convert button top left.
I chose All Grain, Old Recipe type Extract and clicked OK.
The recipe converted to All Grain along with mashing schedule.
Am I wrong?