Divi Theme Change Contact Form Subject Line to remove site name and tagline

divi-change-subject.php

// Instead of creating a custom Contact Form element:
add_filter('gettext', 'edit_divi_contact_form_subject', 10, 3);
function edit_divi_contact_form_subject($translated_text, $text, $domain)
{
    if ($text === 'New Message From %1$s%2$s' && $domain === 'et_builder') {
        return 'New Contact Form Message';
    }
    return $translated_text;
}

// You can also add this CSS to customize the Success message style of the form:

.et-pb-contact-message p {
    font-size: x-large;
    font-style: italic;
    font-weight: 600;
    color: darkgreen;
}