functions.php

function customize_groups_custom_fields( $groups_mapping = array() ) {

	$groups_mapping['group_assistant_leaders'] = array(
		'api_mapping' => 'leaders',
		'data_type' => 'object',
		'child_object' => array(
			'group_assistant_leader' => array(
				'api_mapping' => 'leader',
				'data_type' => 'object',
				'child_object' => array(
					'asst_leader_full_name' => array(
						'api_mapping' => 'full_name',
						'data_type' => 'string'
					),
					'asst_leader_email' => array(
						'api_mapping' => 'email',
						'data_type' => 'string'
					),
				),
			),
		),
	);
	$groups_mapping['group_coach'] = array(
		'api_mapping' => 'coach',
		'data_type' => 'object',
		'child_object' => array(
			'coach_full_name' => array(
				'api_mapping' => 'full_name',
				'data_type' => 'string'
			),
			'coach_email' => array(
				'api_mapping' => 'email',
				'data_type' => 'string'
			)
		)
	);
	return $groups_mapping;
}
add_filter( 'ccb_get_groups_custom_fields_map', 'customize_groups_custom_fields' );