The problem occurs due to system customization limitations. The previewed invoice cannot be fully customized because it includes both validated and non-validated invoices. Customization is only possible for the finalized invoice that gets attached once validation is complete.
Go to Preview Invoice.
Click Settings.
Select the invoice that has been customized.
To add the QR code formula, go to Report, Insert Control, Picture/OLEBound.
Add the following formula to the File column: ADDBS(C_DIRNAME) + "eInvoice.bmp".
Click OK.
Click File, Save As.
Save the file under the name: 'einvoice_inv' in the company database folder.
Once the e-invoicing validation is done, the system will save the customized format as a PDF attachment.