The task of designing and planning an assembly system is complex and challenging. Today, planning results are often dependent on the experience and methodological skills of the planner as well as on the available planning tools available. Digital processes are used to accelerate the planning process and establish the best possible shared knowledge base. Currently, the planning is partly supported by digital tools such as digital models and simulations. A disadvantage of digital modelling and simulation studies is their complex and expensive development. This paper presents a digital and partially automated planning process for the concept planning of an assembly system for a customer-individual product, in which not only the assembly system with its number of workstations is planned, but also the positioning of the required materials at the individual workstations is carried out considering ergonomic aspects. This is demonstrated using the example of a customer-individual last-mile electric vehicle.