Toast the Walnuts: Preheat your oven to 325°F (160°C). Spread the walnut halves on the baking sheet and toast for 8–10 minutes, shaking the pan once, until fragrant and a shade darker. Remove from the oven and, while warm, toss with the smoked paprika. Set aside to cool completely, then roughly chop.
Prepare Produce: While the nuts cool, dice the apples into ½-inch pieces. Slice the celery ribs thinly on a bias, reserving any tender leaves for garnish. Halve the grapes. Place the apples, celery, and grapes into the wide mixing bowl.
Add Fresh Herbs: Add the finely chopped dill and snipped chives to the bowl with the fruit and celery.
Whisk the Dressing: In a separate small bowl, whisk together the labneh, mayonnaise, fresh lemon juice, and maple syrup until smooth.
Combine Salad: Pour the dressing over the apple mixture. Add the cooled, chopped walnuts. Using a spatula, gently fold everything together until evenly coated.
Season and Serve: Sprinkle the sea salt and several grinds of black pepper over the salad and give it one final fold. Taste and adjust seasoning if needed. Transfer to a serving platter and garnish with reserved celery leaves and fresh dill before serving.