Test on any device of your choice. Moodle 3.8 or latest 3.7 version needed. As a teacher, using master, navigate to dev course > Books > A book with some chapters... Open the Table of contents and check some chapters are dimmed and the numberation have x's. Click on one of it and check the numeration on the title corresponds. Use the navigation arrows and check you can go forward, backwards to any chapter of the book. Now enter the same book as student and check the hidden chapters are not there. Moodle 3.6 Export the previous book activity and import it in a 3.6 site Check that as teacher or student you don't see hidden pages