Whisk white wine vinegar, curry powder,and pressed garlic in medium bowl to blend. Gradually whisk in olive oil. Season dressing to taste with salt and freshly ground pepper.
Cook lentils and kohlrabi leaves in heavy large saucepan of boiling salted water until lentils are barely tender but not too soft, about 6 minutes. Drain; rinse under cold water to cool. Drain again.
Bring 1 1/4 cups water to boil in same saucepan; remove from heat. Add 3 tablespoons dressing, sprinkle with salt, then stir in couscous. Cover pot and let stand 5 minutes. Transfer couscous to medium bowl. Fluff couscous with fork to separate grains and cool slightly. Season to taste with salt and pepper.
Meanwhile, transfer lentils to large bowl. Add 1/2 cup dressing, diced kohlrabi bulb, and chopped green onions; toss to coat. Season mixture to taste with salt and pepper.
Arrange baby spinach leaves over large rimmed platter. Drizzle spinach with 2 to 3 tablespoons remaining dressing. Sprinkle spinach leaves with salt and pepper. Mound lentil mixture in center of platter over spinach leaves. Stir mint into couscous. Spoon couscous around lentils and serve with remaining dressing.