Add a Windows Shell context menu entry for a specific extension (not file type)
Here you go:
Windows Registry Editor Version 5.00[HKEY_CLASSES_ROOT\*\shell\your custom app]@="Open with your custom app""icon"="C:\\Windows\\notepad.exe,0""AppliesTo"=".nfo"[HKEY_CLASSES_ROOT\*\shell\your custom app\command]@="C:\\Windows\\notepad.exe \"%1\""The line "AppliesTo"=".nfo" does the trick.
Works perfectly on Windows 10.
It works per file extension, regardless if there is an application associated with that extension or not. Doing this way it less invasive and leaves a very small footprint in the registry.
Compare to Add menu item to windows context menu only for specific filetype
Edit:
If you want to apply that command to more than one extension use:
"AppliesTo"="System.FileName:\"*.nfo\" OR System.FileName:\"*.log\""