One of my children was especially prone to wandering off and no safety belt in a cart could hold her in. I tried the child harness/leash method. The only way that would have worked is if I were willing to drag her through the store. Every time I put it on her she would lay motionless on the floor. It was the only time she was still.
She is now past that phase and we are so thankful that she survived her toddler and preschool years. For awhile I was certain she wouldn’t make it.
Thats the same way cats act.