For the dressing: In a bowl, whisk together the olive oil, mozzarella liquid and pickle juice. Whisk in the vinegar. Taste for seasoning. Set aside.
For the herb salt: Put the parsley and the salt in the bowl of the food processor and pulse to blend until they are integrated and the salt is green. Keep in a sealed jar.
To assemble the salad: Slice and arrange the tomatoes in a single layer on a flat surface. Drizzle the tomatoes with a little sugar, black pepper and the dressing. Top with a sprinkle of the parsley salt. Taste a tomato slice for seasoning. Squeeze the lemon juice on the watermelon. Season the mozzarella slices with parsley salt and a little dressing, as well. Arrange the tomatoes, mozzarella and watermelon cubes on 6 rectangular plates. Serve immediately.