What are the notebook roles?

Four, and the line that matters runs between the first two.

Owner controls the people: adding them, removing them, changing roles, and renaming, deleting or locking the notebook. Manager is a delegated access manager — everything an editor can do, plus setting and clearing restrictions on folders and notes — but it cannot add or remove anybody, or change a role.

Editor writes. Viewer reads.

So manager is the role for somebody organising a shared notebook day to day without handing over the keys to its membership.