v0.62.0
Existing WordPress pages can be moved into a handbook: select them under Pages and pick "Move into the handbook" from the bulk actions. Subpages always come along, and the old addresses keep working through a permanent redirect, because WordPress does not redirect on a post type change. Moved pages arrive as "Not reviewed" until you set a review date.
A bundle can be imported as ordinary WordPress pages instead of handbook pages. The text, the images, the diagrams and the page structure come along; the handbook, the access rule, the navigation, the table of contents, the badges and the review data do not. Those pages are always created as drafts, so a bundle from an internal handbook is never published by the act of importing it.
In the navigation, the first level is indented under the handbook title, so every level is set in by the same step. In wp-admin, the filters above the page list follow the order of the columns they filter, and the duplicate handbook column from 0.61.0 is gone.
Nothing needs doing on update.