When making use of the 'Save document to file location' Method on a SharePoint Library SmartObject, a message will always be displayed stating "The 'Save document to file location' method is no longer available."
With the release of K2 Five, the functionality of the "Save document to file location" method in the SharePoint Service Instance for Library SmartObjects was removed and replaced with the above message.
The reason for this is that the method exposed a potential security risk to the K2 Server.
The decision was made by K2 Product Management to remove the method functionality. The method itself needed to remain to avoid issues with existing SmartObjects that would be inconsistent if the method was simply removed.
The error messages were implemented to inform clients making use of the method that it is no longer available. The intention is to completely remove the method in a future version of K2.
Due to the inherent risk, there is also no other out-of-the-box option available to save files locally to the K2 Server via a SmartObject.