[Variables in Export Persona]

Are there other variables to use besides "Slice Name" when setting up file naming in an export preset? I'm exporting several artboards to PDF and would like my FileName_ to be appended to the beginning of each PDF (not just the SliceName). The two workarounds I've found are:

1. Name each artboard with the filename at the beginning of it (but this is messy and doesn't allow you to see the artboard's name unless my Layers panel is really wide).
2. Manually enter the FileName_ text in front of the SliceName variable in the Export setup, but obviously this is time consuming and prone to errors.

Thanks in advance!