Thank you for the answer. However when I specify the sheet.json in the sandbox I don't see a way to upload or paste the contents of charactermancer.html for the sandbox to use. { "html": "sheet.html", "css": "sheet.css", "authors": "mmpApps Corp", "instructions": "instructions.html", "sheetCharactermancer": { "src": "charactermancer.html", "version": 1, "name": "My Charactermancer" } }