I've noticed that some Windows Phone 8.1 screens like the Microsoft Account sign-in wizard have buttons like "Previous" or "Next" below the soft keyboard. So you can type in whatever into an input field and tap a button to go to the next screen without needing to close the keyboard first. This wasn't just a standard app bar. However I have not been able to find what APIs do this and can't find anything explaining how to do it online.
Has anyone found how to do this? Or is it impossible for a third party app?