Fill a medium pot with water and bring to a boil over medium-high heat.
Add the noodles and cook until tender, about 5 minutes.
Transfer to a colander, rinse with cold water, and set aside.
Meanwhile, add two inches of water to another medium pot and add a basket steamer.
Bring to a simmer over medium heat and add the zucchini, asparagus, and broccolini.
Cover and steam until all the vegetables are bright green and tender, about 3 minutes. Remove from the heat and set aside.
In a small bowl, whisk together the soy sauce, rice vinegar, ginger paste, maple syrup, toasted sesame oil, and garlic until well combined.
In a serving bowl, combine the soba noodles and the vegetables. Drizzle with the dressing and toss to coat. Sprinkle with the chili flakes, if desired, and serve.