Yup, the save data is stored externally; delete this file to delete your save data and start fresh:
- Linux:
~/.lexaloffle/pico-8/cdata/pancelor-make-ten-dx.p8d.txt - OSX:
/Users/YOUR_NAME_HERE/Library/Application Support/pico-8/cdata/pancelor-make-ten-dx.p8d.txt - Windows:
C:/Users/YOUR_NAME_HERE/AppData/Roaming/pico-8/cdata/pancelor-make-ten-dx.p8d.txt