The goal of the HiFlow³ project is to develop a versatile tool that offers the performance and flexibility required to solve large-scale applications efficiently and accurately. The HiFlow³ relies on a holistic approach encompassing the areas of numerical simulation, numerical optimization, hardware aware numerics, high performance computing (HPC) and cloud computing for the solution of complex problems with high relevance in science and impact on society for instance in the fields of meteorology, climate prediction, environment, energy research, medical engineering, and bioinformatics. All these problems have in common a very high complexity of the systems under study, mathematical models with strong couplings, and large requirements of computer resources such as memory and CPU speed. Due to the wide variety of models, assumptions, requirements, and purposes of the problem settings usually different aspects need to be considered in the simulation cycles. To handle this, HiFlow³ aims at maximal flexibility by its modular approach.