at time 9:31, you see that he unscrews a little screw in the middle of the lever. The "cap" in front of it is missing (also at the beginning of the video), so I think it's just glued in, maybe with adhesive tape. Try to lift up the cap with a small blade, or a small flat screwdriver, I think it will come out, then you will reach the screw. Let me know if it works. Good luck !