Placeholder for the root [Node] of a [PackedScene]. Turning on the option [b]Load As Placeholder[/b] for an instanced scene in the editor causes it to be replaced by an [InstancePlaceholder] when running the game. This makes it possible to delay actually loading the scene until calling [method create_instance]. This is useful to avoid loading large scenes all at once by loading parts of it selectively. The [InstancePlaceholder] does not have a transform. This causes any child nodes to be positioned relatively to the [Viewport] from point (0,0), rather than their parent as displayed in the editor. Replacing the placeholder with a scene with a transform will transform children relatively to their parent again. Gets the path to the [PackedScene] resource file that is loaded by default when calling [method create_instance].