EnsLib.File.PassthroughOperation has File Name property with default value: %f_%Q%!+(_a)

The Management Portal documentation description of the property:

Name of file to output the document(s) to. May include timestamp specifiers. The %f specifier if present will be replaced with the name of the document's original source filename (stripped of characters illegal in target filenames).

See the method Ens.Util.File.CreateTimestamp() for documentation of timestamping options.