i.e. todo.txt, medical.txt, etc.
I looked at XML files in
C:\Program Files\Notepad++, but to no avail.
By the way, if you want to know how I found this out, I fired up Sysinternals ProcMon, set a filter on the ProcessName field to "notepad++.exe", closed Notepad++ and then ProcMon showed me which files had been accessed when I closed it.
This location should work regardless of username or Windows version: