In a medium saucepan, combine the rinsed quinoa, water or broth, and salt. Bring to a boil over high heat, then reduce heat to low, cover, and simmer for 15 minutes, or until the liquid is absorbed and the quinoa is fluffy. Remove from heat, fluff with a fork, and let it cool completely (spread on a baking sheet to speed up cooling).
In a small bowl or jar, whisk together the olive oil, apple cider vinegar, maple syrup or honey, Dijon mustard, salt, and pepper until well combined and slightly emulsified.
In a large mixing bowl, combine the cooled quinoa, diced apple, dried cranberries, chopped walnuts, diced celery, and chopped parsley. Toss gently to distribute ingredients evenly.
Pour the dressing over the quinoa mixture. Toss thoroughly until everything is evenly coated. Taste and adjust seasoning with more salt or pepper if needed. Serve immediately in bowls, or refrigerate for 30 minutes to let flavors meld.