Returns the "href" for this publication navigation item if it does not target any location within the publication.
The href can for example refer to an external website (https://<some_website>) , or an email address (mailto:<some_email>)
This property is always null if isTargetingReaderDocumentInSpine is true.
An identifier for this item, unique within the publication.
If the locator is targeting content within the publication.
The locator for this navigation item
The id of the parent navigation item if any. Null if this is a top-level item.
The contents of this item as text.
The nested children of this item if any.