Place the bell pepper, celery, kohlrabi, green onions, parsley, and all but 1/2 cup of the beans into a large serving bowl.
Place the remaining ingredients, including the reserved beans and juice of half a lemon, into a food processor, and blend until smooth. Add this dressing to the bowl and stir well to coat. Refrigerate until well chilled, at least an hour, but better the next day. Check seasonings and add more salt, lemon juice, and za’tar to taste. Serve sprinkled with additional parsley or za’tar.
You can use about a cup of any crunch-providing vegetable or fruit instead of the kohlrabi. Water chestnuts or jicama would provide a neutral flavor while Asian pears or apples would contribute a hint of sweetness.