I created a custom, standard report based on the Stock Ledger and now need to design a print format for it. However, ERPNext only generates a folder with a JSON file on the backend; adding an HTML file doesn’t cause the report to render when printing.
any help or recommendations
Hello 
,
Good news for you!!
You can create, please Read this.
https://docs.frappe.io/framework/user/en/guides/reports-and-printing/print-format-for-reports