Presumably the 's' key (not 'S') has the same result in MEP 2014 for others as it does for me, namely to toggle the media pane on or off? Stumbled aross it by accident.

It works when you are previewing in full screen mode too, and I'm guessing that's its intended purpose, to allow you to change settings from there?

It's not in the list I see at File > Settings > Keyboard shortcut... > List.
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Terry, East Grinstead, UK