This trick is the Gyroscopic Flop. This trick is really interesting, as it's not really a string trick. It rotates the yo-yo around its axis.
To do the Gyroscopic Flop, you start off with the Trapeze. You pinch the string right above the yo-yo, and basically you whip the string around to the outside to your right side. From there, it forms a loop. With that loop, you want to rap into the yo-yo like so. From there, you grab both strings at both sides of the yo-yo and you pull away from the yo-yo at the same time. And when you pull it, the yo-yo will start to twist and spin by itself.
And that's the Gyroscopic Flop.