How do I move a book from one difficulty level to another?

Question

To move a book from one difficulty level to another, see either of the following:

• [How do I change the expected rate of project progress?](http://support.paratext.org/t/how-do-i-change-the-expected-rate-of-project-progress/429)
• [How do I customize Project Progress stages?](http://support.paratext.org/t/how-do-i-customize-project-progress-stages/520) (the Change the difficulty level of a book section)