A newline is a character that moves the text following it down a line. This can be useful for moving HUD texts down the screen, having separate information shown within the same text, and much more.
To add a newline to a string, copy the action containing the string and paste it into a text editor. Type
\n in the string to create a newline. Select everything in your text editor and paste the action back into your actions list. Make sure to remove or disable your original action and move the newly pasted one back into its place.
For console workshoppers, you can use the import code ATP4N to get a newline into your game.
Note: if the first character of your string is a newline, a square character will appear when the string is displayed. To avoid this, simply put a space or other invisible character before a newline if it's the first character.