The current version of Mp3tag has no built in feature to write multiple export files in one run at once.
The Mp3tag mte report file accepts only one command or function $filename(...).
But there are two helper tools available, which probably can work for you ...
Mp3tagSplitList
Mp3tagSplitList
Mp3tagSplitLyricsList
Mp3tagLyricsSplitter
Copying lyrics (tags <-> txt)
DD.20150922.1913.CEST