When we started working on the Lockdown feature we often found that we also wanted to keep certain notebooks private - we'd use them for storing passwords and sharing sensitve data within a project. So we decided that Notebooks too should get the same Lockdown teatment.
Once that was decided we were able to bring the same new streamlined interface to Notebooks. As you can see from the screenshots - gone are the old tabs which hid important information. Instead, everything you need to see is visible at a glance.
Lockdown now enables you to pick exactly who will be able to view the notebook - previously you could only make it private within the owner company. Just think of the huge flexability this offers.