In Dabble, a prologue, epilogue, or other non-chapter section of your novel is a chapter without a number. To add one of these elements to your novel:
Title the chapter with the name "Prologue" (or whatever the item is named)
Click on the chapter label above your title (e.g. "CHAPTER 1") to toggle numbering off
Once you have turned numbering off for this chapter, the chapter label will fade slightly losing its number.
It will only be visible when you hover your mouse over the title and will not be visible on export. In addition, the following chapters will not count this one when determining their chapter number.