Bring a large pot of salted water to a rolling boil and add the dry macaroni noodles. Cook until al dente, about 7–9 minutes, then drain and rinse under cold water.

In a large mixing bowl, combine cooled macaroni, diced corned beef, shredded Swiss cheese, drained sauerkraut, and chopped dill pickles. Gently fold together using a spatula.

In a small bowl, whisk together Thousand Island dressing, mayonnaise, Dijon mustard, and sauerkraut brine until smooth. Adjust seasoning as desired.

Pour dressing over the pasta mixture and stir gently until well coated. Cover and refrigerate for at least 1 hour to allow flavors to meld.

Before serving, taste and adjust seasoning if needed. Serve cold as a main dish or side.