BTW, I am not very happy with the current bindings. I would think that it is better to view/update master by default and has a special binding for child only. This way a same key binding C-r would always view the full document.
I second that motion. I am a master/child user and I am putting item [1] into evidence :-) Hugo[1] https://github.com/apex-hughin/LyX/blob/master/lib/scripts/lyxdocversion.py