Enhance signature block via API

Hi colleagues!!

Does anyone know if it's possible to add a formFields to the default SIGNATURE_BLOCK?

Adobe Sign, by default, is generating a SIGANTURE BLOCK with some fields at the end of the last page...

I need to enhance the SIGNATURE BLOCK with national ID number for example.....

Do you know if it's possible to add the field without to send FormFieldLocation attributes?

I'm testing with PUT /agreements/{agreementId}/formFields method

Regards

Mariano