I'm pretty sure you'd have to do it in Motion. If you own that, just right click the thumbnail of the Title in the Title pane and choose Open in Motion.
In there you could probably do it by duplicating one of the existing bullet layers and dragging the new bullet text where you wanted it, both in the video window and in the Timeline.
Someone here who really knows what they're doing could probably do it in less time than it's taken me to write this
I did once make a variation of this same Title, but did not add more lines. I just spaced the bullets farther apart so there was space for two lines of text per bullet.