I tried that out and I was able to add the yeast to my inventory. However, when I click on the Inventory tag in the recipe and select the yeast from the list, it just scrolls up to the top and does nothing. When I scroll back down to the yeast area, the inventory menu is still open.
I've run into something similar with the custom fermentables, also, it may or may not be unrelated.
Edit: Using Chrome browser
Edit 2: If I click on the brown inventory button, it doesn't let me add it. But it DOES show up in the pull down list of ALL yeasts. I think I may have misunderstood which inventory pull down you were referring to.