Once you have created a proper export script file, which in turn creates one output text file of format XLM or other format, per one track file, then you can apply this export script against each single entry in the Mp3tag listview, step by step.
There is no built in feature in the export section yet, which can create multiple output files at once, one for each input file of a group of files.
But there are two helper applications, which you can try out ...
Dano, Mp3tagLyricsSplitter
Copying lyrics (tags <-> txt)
DetlevD, Mp3tagSplitList
Mp3tagSplitLyricsList
DD.20141111.0753.CET