Add WPCode Custom Field Smart Tag

add_filter( 'wpcode_smart_tags', function( $tags ) {

	$tags['custom'] = array(

		'label' => 'Custom',

		'tags'  => array(

			'custom_field_tag' => array(

				'label' => 'Custom Field Tag',

				'function' => 'wpcode_custom_field_tag',

			),

		),

	);

	return $tags;

} );

function wpcode_custom_field_tag() {

	// Replace custom_field_tag below with the meta key of your custom field.

	return get_post_meta( get_the_ID(), 'custom_field_tag', true );

}