Cut potatoes into ¾-inch chunks. Add to pot with 2 tsp salt and cover with cold water. Boil until tender (8–10 minutes).
While potatoes cook, prep the eggs, pickles, celery, shallot, scallions, and herbs.
In a bowl, combine eggs, pickles, celery, shallot, scallions, herbs, remaining salt, mayo, mustard, and 1 tbsp vinegar.
Drain potatoes and spread on a tray. Sprinkle remaining vinegar. Cool for 15 minutes.
Add cooled potatoes to dressing and fold gently to combine.
Taste and season with more salt and pepper if needed.
Cover and refrigerate at least 1 hour before serving.
