You can unpublish (i.e. hide) a chapter so that end users cannot see the content. This article will teach you how to make an unpublished/hidden chapter visible to your end users in your manual.
The option will say Publish if the chapter is currently unpublished and it will say Unpublish if it is currently published.
Upon publishing/unpublishing a chapter, you'll be given the option to either affect all of the articles in the chapter at the same time or to just the chapter itself (see below).
In the case of unpublishing, the later option means that the chapter will not appear to end-users while they browse your knowledge base, but articles within the chapter will still appear in search results.