Cannot connect SmartThings device to harmony hub button

I just bought the SmartThings hub and a Wemo plug. I have all of that working great. I can turn the Wemo plug on/off through the SmartThings app. I then connected SmartThings to my harmony hub account, and added the Wemo plug. I see the plug in the home control devices. I can turn it on and off through the devices list in the harmony app. I even set it up in the start and end sequences of the activity. The plugs works correctly when the activity is turned on and off. When I try to bind the plug to a button, it is not in the list. Should it be? Is that possible, or a limitation?