What are the limitations of the signature field in Vtiger?

There are several limitations:

• The Signature field is not supported in the Documents module, Webforms, or Mailroom actions.
• It cannot be made a header field, and only one Signature field can be added per module.
• Signatures cannot be directly edited in Grid view, imported, or uploaded as an image file.
• Once saved, a signature cannot be edited but can be replaced or deleted with a new one.
• Masking functionality is not available for the Signature field.