In a large pot over medium-high heat, combine chicken, broth, and 1 tablespoon plus 1 ½ teaspoons seasoned salt. Bring to a boil, then reduce heat to medium, cover pot, and cook until chicken is cooked through, about 10 minutes. Transfer chicken to a cutting board. Let rest 5 minutes.
Meanwhile, in a large bowl, stir yogurt, mayonnaise, parsley, dill, mustard, lemon zest, and lemon juice until smooth.
Cut chicken into ¼" cubes and add to yogurt mixture, tossing to coat. Add celery, onion, pickles, pepper, and remaining 1 ½ teaspoons salt and mix until well combined.
