Hi,
One way that you can do this, so that it is controlled in your inventory is to add your DME into your recipe. So that it doesn't add to your OG, you need to double click on it after you add it and zero out the value in the potential field. (I tried checking the non-fermentable box, but it does not work). Also, check the box for "Add after boil" so that you don't accidentally add it early in the process.
It's a work around, but it will let you manage how much is taken from inventory.
-Dan