In the newest version of game maker you cannot import it. gives the following error:
Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object. at ProjectTool.ProjectLoader.Load(String& _path, String _format, String resourceTypesPath, String environmentPackagesFolderPath) at ProjectTool.Commands.ProjectSaveCommand.Execute() at ProjectTool.Program.Main(String[] args)
Been using it for years so it's unfortunate.