From https://vincent.re/en/open-containing-folder-in-notepad
To assign the command to a shortcut. Open %APPDATA%\Notepad++\shortcuts.xml
with an editor. In the <Macros>
tag add the following for Ctrl+Shift+O
<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>
So for example, my file will look like this after
<NotepadPlus>
<InternalCommands />
<Macros>
<Macro …>…</Macro>
<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>
</Macros>
<UserDefinedCommands>
<Command…>…</Command>
</UserDefinedCommands>
<PluginCommands />
<ScintillaKeys />
</NotepadPlus>