Boil the potatoes in salted water until fork-tender (about 15 minutes). Drain and let cool completely or almost if you're impatient. No need to peel them, just make sure they’re clean.
Chop the pickles, chives, parsley, and red onion. Mix the red onion with a squeeze of lemon juice and a pinch of salt, then set aside to marinate.
In a bowl, mix the pickle juice, mayonnaise, mustard, salt, pepper, and olive oil.
Cut the cooled potatoes into large chunks so they hold their shape well. Add the potatoes, chopped herbs, pickles, red onion, and sauce to a large bowl. Toss to coat.
Taste and adjust seasoning as needed. Chill before serving for best flavor.