There’s a lot of wisdom in that video about Sally Bell’s.
(I wish we could find someone who’s tasted their potato salad, and knows why folks will line up for an hour to get it - must be something more than just having someone else make it for you ;-)
I did a search. Pickle juice and lots of celery seed.
It’s a guess recipe ... but here it is:
Sally Bell Potato Salad
I haven’t had the potato salad there. I am picky about potato salad, hate eggs in it, so have never tried it.
A good potato salad can be amazing. I am partial to the German version, having eaten it all my life. No mayo and lots of vinegar. To get the sour flavor to stay, right after you strain your boiled to al dente peeled potatoes, you sprinkle in the vinegar. To be eaten warm or cooled (your gut bugs crave cooled potatoes so that’s a plus - when they are happy you will be happy).
But I’m still American and the mayo potato salads, made just right with a few added ingredients, still make me happy. Some mustard maybe, some capers or sour pickled something all up in there, even hard boiled eggs. It’s good. But I might avoid it at a hot picnic.