iA Writer 3 has new shortcuts to help you structure your text. You can use the easy to remember ⌥⌘↑ and ⌥⌘↓ or, if you are accustomed to other text editors, ⌥⌘] and ⌥⌘[ respectively.
MultiMarkdown metadata variables provide simple, powerful text references. Build your own correspondence templates:
iA Writer for iOS lets you add the functions you use most to the keyboard: