Domain experts with their special knowledge and understanding of a specific field are critical in the development of chatbots. However, engaging domain experts in the chatbot development is time-consuming and cumbersome because developers lack adequate systems. We address this problem by proposing three design principles for interactive chatbot development systems grounded in the interactivity effects model. We instantiate the proposed design and evaluate the resulting artifact in an online experiment. The results of the online experiment (N=70) show that the proposed design significantly increases subjective and objective engagement and that perceived interactivity mediates these effects. Our study contributes with prescriptive knowledge for designing interactive systems that increase engagement and with a novel artifact in the form of an interactive chatbot development system.