Energy flexibility is key to integrating more renewables into the grid. An essential contributor to enabling energy flexibility is P2X technologies such a Power2Heat, Power2Gas, among others. To evaluate the flexibility available from these resources and the impact they can have on the electrical grid, complex simulations need to be set up that may not always be possible using traditional simulation tools, given the multi-domain nature of such systems. Hence, the need for intelligent simulation techniques arises. This paper introduces a co-simulation tool, FMUWorld, to overcome simulation problems for complex energy systems. We use a multi-energy co-simulation and an energy flexibility analysis as use cases to explore the capabilities of the proposed tool. The ease-of-use offered by FMUWorld is shown to allow users to focus more on analysis of the system, such as parameter sensitivity, system optimisation, etc., rather than co-simulation setup. The paper highlights the key features and functionalities of FMUWorld that make it a novel tool for cosimulation of multi-energy systems.