There is no built-in save functionality but you might be able to obtain some utility services from webMethods support or professional services.
The savePipelineToFile method saves the pipeline variables at a specific point in your flow into a special directory on the server(ie. all the strings and objects in your flow) webMethods uses a special XML file to load and save these variables. It’s not for saving your own files to disk. You need your own java service for this.
#Integration-Server-and-ESB#webMethods#webmethods-Protocol-and-Transport