The «Grand Plan». Nature and Function of Leibniz’s Demonstrationes Catholicae

From a young age, Leibniz worked on an ambitious project, for which he wrote an initial -summary under the title Demonstrationum Catholicarum conspectus («A Prospect of Catholic Demonstrations»). This was the first iteration of a recurring project which scholars such as Heinrich Schepers and (especially) Maria Rosa Antognazza have designated as his most significant «plan», encompassing natural theology, Christian unity, logic as a universal science, and a comprehensive encyclopaedia written in a formal language. What were the real features and functions of this «plan»?