@Nicolas Bean I'm studying for the multi-book cert and this use case is called out explicitly not "solved or supported" by multibook. They suggest that you can use report builder to create a custom report that runs on a different base period than your subsidiary (https://netsuite.custhelp.com/app/answers/detail/a_id/7658) but I haven't done that myself.

that is wha tI thought, thanks for letting me know! I am studying as well and am looking to pass my enablement next week