You are aware that CKEditor has built in hotkey functionality?
It's pretty straightforward to implement: You set up an array keystrokes
in your config array; take the example array from the link above; Look up the keystroke for "S"; and amend the array by an entry for it, and the appropriate CKEditor command. I can't test it right now but this is what it should look like. You may need to look up the appropriate command for the "save" operation you want to execute.
... your config array .....
"keystrokes":
[
[ CKEDITOR.ALT + 121 /*F10*/, 'toolbarFocus' ],
[ CKEDITOR.ALT + 122 /*F11*/, 'elementsPathFocus' ],
[ CKEDITOR.SHIFT + 121 /*F10*/, 'contextMenu' ],
[ CKEDITOR.CTRL + 90 /*Z*/, 'undo' ],
[ CKEDITOR.CTRL + 89 /*Y*/, 'redo' ],
[ CKEDITOR.CTRL + CKEDITOR.SHIFT + 90 /*Z*/, 'redo' ],
[ CKEDITOR.CTRL + 76 /*L*/, 'link' ],
[ CKEDITOR.CTRL + 66 /*B*/, 'bold' ],
[ CKEDITOR.CTRL + 73 /*I*/, 'italic' ],
[ CKEDITOR.CTRL + 85 /*U*/, 'underline' ],
[ CKEDITOR.CTRL + 83 /*S*/, 'save' ],
[ CKEDITOR.ALT + 109 /*-*/, 'toolbarCollapse' ]
];