This is a reference for every control in the Manuscript Editor toolbar. You don't need any of it to start writing; hover over a button to see its name.

Font & style
Font Family and Font Size
Text Color and Highlight Color
Clear Formatting: returns the selection to plain text.
Format Painter: copies the formatting of the selected text. While it's active, click the text you want to apply it to.
Headings
Heading 1 to Heading 4 apply to the current line or selection.
Text formatting
Bold (Ctrl + B), Italic (Ctrl + I), Underline (Ctrl + U) and Strikethrough.
Alignment & lists
Align Left, Align Right, Align Center, Justify, Bullet List and Numbered List.
Structure & inserts
Blockquote
Horizontal Rule: a scene or section break.
Insert Link, and Remove Link when your cursor is on a link.
Insert Image
Undo & redo
Undo (Ctrl + Z) and Redo (Ctrl + Y).
Export
Export DOCX and Export PDF open a dialog where you choose which sections to include. Export is available on paid plans, and you'll be asked to set up two-factor authentication before your first export (see Setting Up Two-Factor Authentication).
View
Focus Mode: a distraction-free, full-screen view. See Distraction-Free Mode.
Notes Panel: show or hide the panel on the right.
Show/Hide Ruler: only when the page has room for its full 8.5 inches. On a smaller screen, or when the sidebar or Notes Panel leaves too little room, the ruler and this button are hidden.
Zoom: change the zoom level, or choose Reset Zoom (100%).
Versions
Create Version saves a restore point for the section, and Restore Version rolls back to one. Version history is available on paid plans. See Manuscript Versioning.
Smaller screens and mobile
On narrower windows (under about 1,000 pixels wide) and on phones, the toolbar starts collapsed to keep the page clear. It shows just a few controls and a Format button; tap Format (or Expand Formatting) to open the full set, and the arrow button to collapse it again.

On a tablet or a narrow window, the page narrows to fit the space, so your text wraps instead of running off the screen.
On phones, the expanded toolbar groups related tools behind single icons (font, text, alignment and lists, structure, undo, view, and export and versions). Tap an icon to see its tools. If not every group fits on your screen, swipe the toolbar sideways to reach the rest.