Ill give that a go
I had a similar question and there is a solution link on this thread.
This is for Hot Folders but the prinicipal is the same as long as you have set up the windows credentials correctly to log into the external server you can then paste the URI in the save node:
UNC: Available by typing the path in the location field. The path must be a valid URI pointing to a shared windows folder.
Is there a walkthrough on how to set a save destination on an external server, ie not the freeflow core server