According to the source code, the XML tag 'filename' is extracted from the incoming request to get a wild card expression to list only the files matching it, but it is not used when listing files. Moreover, the associated MONIT trace 'providerExtBegin' contains an attribute associated to the wild card expression used to list files.
Note: The wild card support is not documented into the user documentation.
So, please, it will be interesting to be able to support a wild card expression if provided.