How to use default Attachment Id in Send Email quick action in LWC component?

Question

I am using below code in LWC to show send email quick action from LWC component

here I am able to set the default value of Subject and Body. But I am not able to attach a default pdf file to this send email.

I tried using Attachment: '0698J000000oPAfQAM' but no success. I couldn't find in any Salesforce documentation as well.

handleClick(emailtemp) {
    var pageRef = {
        type: "standard__quickAction",
        attributes: {
            apiName: "Case.Send_Email_New"
        },
        state: {
            recordId: this.recordId,
            defaultFieldValues:
            encodeDefaultFieldValues({
                HtmlBody   : emailtemp.HtmlValue, 
                Subject : emailtemp.Subject,
                Attachment: '0698J000000oPAfQAM'
            })
        }
    };

    this[NavigationMixin.Navigate](pageRef);
}