Hi psucom,
the scorefile is part of the large flashcards SQLite database.
You could back up your flashcards database, copy it onto a Mac or PC, then use a free SQLite reader of your choice to export the scorefile data or, better yet, write a Python script that accesses the flashcards SQLite database and gives you a list of all the flashcards in a particular category along with the study history for each flashcard. This should be quite easy to do with Python and is well-documented. However, if the flashcards aren't custom flashcards, you probably wouldn't be getting the flashcards' contents with the export, because that data isn't in the flashcards database, but in the dictionaries. So that would require a Pleco feature, as far as I can tell.
Perhaps Mike can tell you even more?
Cheers,
Shun