One of the camera settings in Smart Shooter is for the camera's program mode. As with other camera settings, the UI that the app presents is driven by information from the camera. The app will query the camera for each camera setting, to get the valid range of values, and whether or not each particular camera setting can be changed.
For Program Mode, most cameras do not allow you to change this from software, hence why the app will disable the dropdown menu. This is usually because the Program Mode is a physical dial switch on the camera, so the only way to change it is to physically rotate that dial.
Exceptions to this are the higher end cameras, such as Nikon D810, which do not have a dial on the camera but instead an electronic button. So for such cameras, Smart Shooter does allow you to change Program Mode in the app.