The API isn't final, afaik, even after almost three years of SailfishOS. Because of it, it is a mess. Harbour apps cannot use it, so if you want to publish your app in Harbour, this method will not be accepted anyway. I wonder if Jolla still believes this is the way forward.

And frankly I agree with pichlo, to change a simple setting all the way via the settiings app, scroll all the way to the bottom, then find the app again in the grid, is way too cumbersome.