I have Visual Studio 2015 Isolated Shell app and i have enabled private galleries by setting enable value as per instruction in application.pkgdef
"EnablePrivateGalleries"=dword:00000000
But unable to see option to configure in Extension Manager dialog
It should be: "EnablePrivateGalleries"=dword:00000001
// Support for end-user customization of extension galleries is disabled by default.
// Uncomment the following to enable end-user customization of extension galleries
// that appear in the Extension Manager dialog.
"EnablePrivateGalleries"=dword:00000001