Widget Navigation Does Not Work Diagonally

There is no such thing, as far as I know. Your widgets should be somewhat aligned in the list for the sake of ease of readability. Maybe you can wrap them up with another focusable widget, and then make sure all of them are of the same size?

If you are talking about Add new, or Back button. You can easily add manual navigation there. Create custom method that will focus to the custom widget in the list.