Add Open with Notepad context menu.

NotepadContext.inf

[version]
signature="$CHICAGO$"

[NotepadContextInstall]
CopyFiles = NotepadContext.Files.Inf
AddReg    = NotepadContext.AddReg

[DefaultInstall]
CopyFiles = NotepadContext.Files.Inf
AddReg    = NotepadContext.AddReg

[DefaultUnInstall]
DelFiles  = NotepadContext.Files.Inf
DelReg    = NotepadContext.DelReg

[SourceDisksNames]
55="Open with Notepad (as Admin)","",1

[SourceDisksFiles]
NotepadContext.INF=55

[DestinationDirs]
NotepadContext.Files.Inf = 17

[NotepadContext.Files.Inf]
NotepadContext.INF

[NotepadContext.AddReg]
HKLM,%UDHERE%,DisplayName,,"%NotepadContextName%"
HKLM,%UDHERE%,UninstallString,,"rundll32.exe syssetup.dll, SetupInfObjectInstallAction DefaultUninstall 132 %17%\NotepadContext.inf"
HKCR,*\Shell\runas,,,"%NotepadContextAccel%"
HKCR,*\Shell\runas\command,,,"%11%\notepad.exe ""%1"""

[NotepadContext.DelReg]
HKLM,%UDHERE%
HKCR,Directory\Shell\runas
HKCR,Drive\Shell\runas

[Strings]
NotepadContextName="Open with Notepad (as Admin) PowerToy (Uninstall only)"
NotepadContextAccel="Open with Notepad (as Admin)"
UDHERE="Software\Microsoft\Windows\CurrentVersion\Uninstall\NotepadContext"

NotepadContext.reg

Windows Registry Editor Version 5.00

; created by Walter Glenn
; for How-To Geek
; article: http://www.howtogeek.com/281490/how-to-add-open-with-notepad-to-the-windows-context-menu-for-all-files/

[HKEY_CLASSES_ROOT\*\shell\Open with Notepad\command]
@="notepad.exe %1"