Split text box for entry animations

(Storyline 360)
I've read something about the "right arrow" will automatically split a text box into multiple layers so that they can be timed to narration.

I've been unable to make this happen.

Here is what I was looking at, but it doesn't really make the details of it clear. https://community.articulate.com/discussions/articulate-storyline/timing-bulleted-list-with-narration

Is this a documented feature somewhere? If not, what is the secret?

Thanks for any help.