Bring vegetable broth to a boil in a saucepan. Add quinoa, reduce heat to medium, and simmer, stirring occasionally, until quinoa is tender and liquid is absorbed, 10 to 15 minutes. Remove saucepan from heat and cool.
Mix cabbage, carrots, edamame, and green onions together in a large bowl.
Whisk vinegar, oil, Sriracha sauce, soy sauce, ginger, sugar, and mustard together in a bowl until dressing is smooth; drizzle over cabbage mixture. Stir quinoa into salad and toss to coat. Refrigerate until chilled, at least 30 minutes.