Isso pode ser feito facilmente usando o PowerShell
New-PSDrive -Name HKCR -PSProvider Registry -Root HKEY_CLASSES_ROOT
New-ItemProperty -Path "HKCR:\SystemFileAssociations\image\shell\edit\command" -Name "(Default)" -PropertyType ExpandString -Value '"C:\Program Files\Adobe\Adobe Photoshop CC 2015.5\Photoshop.exe" "%1"'