The transition to decentralized urban energy systems requires simulation tools capable of capturing interactions across electrical, thermal, and building domains. Although recent web-based platforms have improved accessibility, defining the logical relationships between heterogeneous models remains complex and is often reserved for domain experts. Existing interfaces typically rely on rigid forms or static dashboards, which struggle to represent the dynamic, interconnected structure of multi-energy systems and the data dependencies required for co-simulation. This thesis presents the development of the Coesi-UrbanSim Frontend, a web-based platform that introduces a node-based visual programming paradigm for urban energy co-simulation. The proposed interface provides a graphical canvas where users compose simulation workflows by linking physical entities, data sources, and simulation models through typed connections.