Adds new elements to a Folder or Document that has already been loaded via a . The element in specifies the URL of the .kml or .kmz file that contained the original Folder or Document. Within that file, the Folder or Document that is to contain the new data must already have an explicit id defined for it. This id is referenced as the targetId attribute of the Folder or Document within that contains the element to be added.
Once an object has been created and loaded into Google Earth, it takes on the URL of the original parent Document of Folder. To perform subsequent updates to objects added with this Update/Create mechanism, set to the URL of the original Document or Folder (not the URL of the file that loaded the intervening updates).