Finishes: Colors & Stains

Actually this is quite easy  the Option key is your friend here. If you hold down the Option key (or the Alt key on a standard keyboard) while you press the Enter/Return key, that will add the blank line to separate the text in a single text message.

If you type [Enter] you'll send your message, but the [alt][Enter] keystroke combination lets you add new lines and create a new paragraph.