how to detach parking brake cable

There's a long spring wound around the cable where it attaches to the lever. That spring is what keeps the cable from falling off that lever. The easiest way to remove it is to grab it near the lever with a needle nose pliers, pull it forward, away from the lever about an inch, then squeeze the pliers to grab the cable and hold the spring there. Now you can twist the cable to pull it off the lever.