This activity is documented here: http://tech.teradp.com/tech/html/gn4/docs/VSdoc/frlrfTeraDPGN4WorkflowActivitySaveXmlClassTopic_members--.html
Note
The SaveXml acitivity can be associated to a XmlTransformOptions (as the TransfomXml activity).
So, if you need to take a story in XML and convert it to plain text and then export it using a workflow, you can put all the conversion xsl into the XmlTransformOptions of the ‘SaveXml’ activity (that is, using it as a TransformXml activity) and then storing the DataOut file with a Save activity.