you can’t exclude a certain chapter from publishing. But you can do the same you’d do to prevent a learner from accessing a chapter. Move it to the end of the title and disable the Next button on the last page your SME is supposed to see. The chapter will of course be published along with the rest of the course but the user won’t be able to reach it.
Instead of a big red button I usually insert a normal table of contents (dropdown) and exclude the chapters / pages a reviewer should not reach directly. So there’s one object with a list of (not necessarily red) buttons, that can be made invisible or moved out of view when the course is ready for the learners.