ifThen(
     parentId,
     (
        $userId = record\attribute(parentType, parentId, 'assignedUserId');

        ifThen(
            $userId,
            (
                entity\addLinkMultipleId(
                    'assignedUsers',
                    $userId
                );

                entity\addLinkMultipleId(
                    'users',
                    $userId
                );
            )
        );
    )
);