Custom Header / Sending with AWS SES SMTP

Anyone can help with setting up AWS with Smartlead?

This video gave me some direction:

https://helpcenter.smartlead.ai/en/articles/143-how-to-make-amazon-ses-work-with-smartlead

Yet, it looks like I need a custom header to invoke the config set in AWS to trigger the Lambda.

I was trying to define a custom header using the API, following a chat with support, but the callback is:

{
"statusCode": 400,
"error": "Bad Request",
"message": ""sequences[0].seq_variants[0].headers" is not allowed",
"validation": {
"source": "body",
"keys": [
"sequences.0.seq_variants.0.headers"
]
}
}

I hope you guys can help me with this.

Thanks,

Cohav