From Jan Berinstein at CompuSavvy:

In a recent blog post, I provided instructions for bypassing the so-called Backstage view (i.e., the File tab’s Open screen / menu) when opening a file with Word 2013 or Word 2016.  I suggested using the keyboard shortcut Ctrl F12, which takes you directly to the Open dialog in Windows.  That keyboard shortcut comes in […]
https://compusavvy.wordpress.com/2015/11/26/reassigning-ctrl-o-to-file-open-in-word-2013-and-word-2016/