Has anybody successfully add a chapter in a Book on Moodle 3.4?
I can not find the plus mark which I was used to in the former version.
Have you got the editing turned on in your course? Have a look at this video, at around two minutes fifteen seconds
Finally, I found out that the problem was caused by the administrator. He hided the plus mark because he want to make the interface clean. And I solved it after I selected a new theme.