The Book

In Notepad++ under Menu → <fc #ff0000>Run</fc> → <fc #ff0000>Run F5</fc> you can put external files that could be run within the editor. Just fill the dialog box with the program name, press <fc #4682b4>Save</fc> and give the shortcut a name.

Shortcuts are saved in

%APPDATA%\Notepad++\shortcuts.xml

under <UserDefinedCommands> and lloks like this

<UserDefinedCommands>
  <Command name="Get PHP help" Ctrl="no" Alt="yes" Shift="no" Key="112">http://www.php.net/$(CURRENT_WORD)</Command>
  <Command name="Wikipedia Search" Ctrl="no" Alt="yes" Shift="no" Key="114">https://en.wikipedia.org/wiki/Special:Search?search=$(CURRENT_WORD)</Command>
  <Command name="Open file in another instance" Ctrl="no" Alt="yes" Shift="no" Key="117">$(NPP_FULL_FILE_PATH) $(CURRENT_WORD) -nosession -multiInst</Command>
  <Command name="Session 01" Ctrl="no" Alt="no" Shift="no" Key="0">$(NPP_FULL_FILE_PATH) "C:\Program Files (x86)\Notepad++\session_01.ses" -multiInst</Command>
  <Command name="Session 02" Ctrl="no" Alt="no" Shift="no" Key="0">$(NPP_FULL_FILE_PATH) "C:\Program Files (x86)\Notepad++\session_02.ses" -multiInst</Command>
</UserDefinedCommands>

As you can see in last two lines, here you can start a new instance of Notepad with predefined files saved in session file.