It's possible to create chapter and scene breaks while writing, directly in your manuscript. So, if you want to create a scene break so that you can move sections of text around more easily, or split a section of text so that it becomes a new chapter, here's how:
Long-click (hold the right side mouse down for 2 seconds) at the point where you want to create the break to bring up the toolbar:
Selecting the button to split a scene (--) or chapter (Ch):
You can also use a shortcut to create scenes and chapters:
Ctrl-enter creates a scene break
Alt-enter creates a chapter break