Chop the cucumber, tomato, and red onion into small pieces. If you're adding bell peppers, grape tomatoes, or green onion, prep those as well.
Drain and rinse the black beans and chickpeas under cold water using a colander.
In a large mixing bowl, combine all the chopped vegetables, rinsed beans, olives, and parmesan cheese.
In a small bowl, whisk together the olive oil, red wine vinegar, Dijon mustard, garlic paste, salt, and pepper. Add any optional ingredients like garlic powder, lemon juice, or maple syrup.
Pour the dressing over the salad and toss everything together until well coated.
Refrigerate the salad for at least 30 minutes to let the flavors blend. Store leftovers in an airtight container and enjoy within a few days.