Thanks for your contributions!
I know this is a extremely old thread, but I just came across this while looking for ways to add keyboard short cut to the "Show Unsaved Changes…" item in the context menu. In Sublime Text 3, most of resources are hidden in the archive, so the Default/Context.sublime-menu file is no where to be found. I'm adding this here in case someone else is looking for the same information about context menu shortcut.
To get to the file, one should install https://packagecontrol.io/packages/PackageResourceViewer and open the resource Default to find the Context.sublime-menu file. For my case, one should open the Diff resource instead.