That's not even hosted on Itch. Why ask here? The chances anyone at all is using it are tiny. I'm going to move this to the tabletop game section, just in case. But your best best is to contact the tool's creator on Twitter and/or Patreon and ask there.
To answer your question, the generator has a prominent Save Image button, and the premium-only features are listed right below. They don't seem to include saving the data in any other format. What gave you the idea such a feature exists?