Notepad++ is one of the bests text editor. Since some versions, it is not possible to open the containing folder of a file with a keyboard shortcut. A simple modification in a config file can fix this.
Open this file with an editor :
%APPDATA%\Notepad++\shortcuts.xml
Inside this markup <Macros> add this :
<Macro name="Open Containing Folder in Explorer" Ctrl="yes" Alt="no" Shift="yes" Key="79">
<Action type="2" message="0" wParam="41019" lParam="0" sParam="" />
</Macro>
Relaunch Notepad++ and then Ctrl + Shift + O should open the containing folder in Windows Explorer.