By default, Mailcoach uses a plain textarea field to edit campaigns and templates. If you'd like to use a feature rich editor, you can install one of the add-on packages.
Unlayer: a drag and drop editor that requires no knowledge of html
Monaco: a powerful code editor that offers syntax highlighting and auto completion.
Other editors can be supported by writing your own editor class. If you feel you've created an editor class that can be useful for other, let us know, and we'll consider packaging it, and adding it to our docs.