Hi Macropod, thanks so much for your reply!
However I'm using a Macbook Pro and I don't have an Alt key.
I tried doing Ctrl+Command+Enter instead but that didn't work.
Would you happen to know the keyboard shortcut for a Style Separator for a Mac, or else how to apply it using the program?

Edit: I noticed my keyboard has an Option/Alt key, so I tried Ctrl+Alt/Option+Enter but I don't believe it worked because it just inserted a new line (the way it would if I had just pressed Enter alone)