Tables, code and quotes
The slash menu that inserts blocks, the toolbar that edits tables, and the rules that keep them compatible with Markdown.
The slash menu
Type / at the start of an empty line and a menu offers the blocks you can insert: Table, Code, Image, Image URL and Quote. Keep typing to filter it, move with the arrow keys, and press EnterEnter to insert or EscEsc to dismiss it.

Tables
A table is inserted with three columns and three rows, the first of them a header. While the cursor is in a table, a toolbar at the bottom of the window adds and removes rows and columns: Add row above, Add row below, Add column before, Add column after, Delete row, Delete column and Delete table.

Two rules keep tables compatible with Markdown, where a table is a grid of plain cells: a cell holds one paragraph, and columns are not resized by hand. A table wider than the text column is drawn wider than the text, so it does not squeeze its columns.
Code
A code block (``` on its own line, or the slash menu) is set in a monospaced font and kept exactly as typed: no smart quotes, no Markdown shortcuts, no comments inside it. There is no language selector, but a language written in a Markdown file (```js) is kept through saves, so highlighting works wherever the file is published.
For a word or two of code inside a sentence, wrap them in backticks or press Ctrl+Shift+K⇧⌘K.
Quotes
Start a line with > to make it a quote, or use the quote button on the toolbar (Ctrl+Shift+B⇧⌘B). Quotes can hold several paragraphs; EnterEnter on an empty line leaves the quote.
More in Writing
The Markdown shortcuts that turn into headings, lists and emphasis while you type, and the ones you can turn off.
The small toolbar that appears over selected text, and the reminder of shortcuts that shows when you hold Ctrl or Cmd.
Six levels of heading, the panel that lists them, and the keys that move through it without touching the mouse.
Bulleted, numbered and checklist items, nesting them with Tab, and turning one kind of list into another.
Links to web pages, to other documents on your disk and to headings in the same document, and how to follow them.
Four ways to put a picture in a document, the difference between embedding and linking one, and what the editor does not do with images.
Notes attached to a passage, in three colours, which travel with the document and never print.
Curly quotes, dashes, ellipses and arrows written for you as you type, the quotation marks of your language, and how to turn each one off.
The spell checker and its languages on each system, adding words to the dictionary, and the language of the app itself.
Right-to-left writing for Arabic, Hebrew, Persian and other scripts, per document or for every new document.
Searching the document or every open tab, and a replace that keeps the capitals of what it finds.
What happens to formatting when text comes in from elsewhere or goes out, and the two ways to copy a document as code.
Calmly Writer