ssa-mailchimp-custom-merge-tags.php

add_filter( 'ssa_mailchimp_subscriber_data', 'ssa_set_custom_mailchimp_merge_fields', 10, 3 );
function ssa_set_custom_mailchimp_merge_fields( $subscriber_data, $customer_information, $appointment_type_id ) {

	$subscriber_data['merge_fields']['SITUATION'] = $customer_information['Current Situation'];

	return $subscriber_data;
}