If after a few minutes nothing is working I just leave Kennedy to her meltdown. You want to scream for 20 minutes have at it I have head phones and just go about what I am doing like she isn’t on the floor screaming. I have even gone as far as mopping around her. She eventually realizes it’s getting her no where and stops

My son used to run away from me when we were at the stores because he liked to browse through the blu-rays and dvds. When he was 6 or 7 I told him to help me push the cart while shopping. Another tip is to go to the store early, before it gets crowded, or near closing times.
We used to go to diners at 3:00 PM for a late lunch or early dinner because it wasn’t crowded.

I agree- we have a portable meltdown kit. If it happens in public , it happens. Try not to care what people think. Just help your child through it.
In our kit we have sensory brushes, monkey noodles, chewies, playdoh, calming smelling lotion, bubbles and a sucker. My guy is prone to throw things when upset so they are softer calm down items.

Chewey or fidget spinner. Both have greatly shortened public meltdowns. Over time I have learned to read my kids and can usually get something in their hands, or get them out of a stressful situation before it gets to a meltdown.

Swinging, walks space, space and quiet, Liam likes songs from the musical Grease, astromania dance, and some baby mozart videos. Car rides work often if all else fails..... We briefly had some luck with a weighted sensory vest but after a few months he wouldn't wear it. He still likes a weighted blanket sometimes.