The editor.

Most manuscripts are drafted in a text box that looks nothing like the book they will become, and the difference shows up late, usually when the first proof arrives and a chapter that read well on screen turns out to be four pages of unbroken paragraph. Draftline's writing surface is a floating page set in Merriweather, with indented paragraphs, a ruled chapter heading, and the ⁂ scene break, so that what you see while drafting is close to what a reader will hold.

Chapter Twelve

The docking clamps released with a sound like a held breath let go. Mara counted the seconds the way her first captain had taught her — not to the jump, but to the moment the jump could no longer be called off.

Four. Three.

On the Harmony, the string quartet had finally stopped playing.

The page.

The chrome around the page stays small so the text carries the screen. You set the font, size, and line height once in Settings, and the page keeps the conventions the printed book will use, which means the scene break you type is the same ⁂ that appears in the exported EPUB and the chapter heading is a real heading that the exporter recognizes rather than a line you made bold.

Bold, italics, underline, superscript and subscript, lists, and text alignment cover what prose needs.

Manuscript structure.

A book is not one long file. The manuscript panel keeps front matter, body, and back matter as three color-coded sections, and you add a prologue, a dedication, or an appendix as a typed item in the right one rather than as a chapter with a misleading name. You drag chapters to reorder them, give any chapter a subtitle, and read the running word count at the bottom of the list.

Copyright Page
Author's Note
Prologue
Chapter 1
Chapter 2
Chapter 3Start editing HERE
Acknowledgments
70,733 words total

Working in it.

Scene breaks and headings
The ⁂ scene break, the chapter rule, and the paragraph indent are structure in the file rather than formatting on the screen, which is why they survive export to EPUB and DOCX intact and why an imported book with a horizontal rule between scenes arrives with the same break in place.
Auto theme
If you leave the theme on automatic, the studio follows sunrise and sunset at your location and crossfades to dark as the light goes, then back at dawn, so the page you look at in the evening is not the one that suited the afternoon. You can also fix it to light or dark.
Chapter subtitles
Each chapter can carry a subtitle that shows in the manuscript panel under its title. Writers use it for the working title of the chapter, a date in the story, or a note to themselves such as "Start editing HERE," and because it is part of the chapter it stays with the chapter when you reorder the book.