Does anyone know how to update only one key-pair in a SSM Secrets Manager secret using terraform or with the AWS Step Functions using service integrations?

I would like to avoid recreating the secret. So for example if my secrets manager secret was

{
   url: google.com,
   fname: jeff,
   lname: smith
}

I might want to update it to be:

{
   url: amazon.com,
   fname: jeff,
   lname: smith
}