Mass customization is a rapidly growing business model that enables companies to deliver products with increased customer value. The ability to design and manufacture highly customer adapted products brings a competitive edge to manufacturing companies and is required for business success in some areas. In this paper, an approach for documentation and knowledge management of systems supporting the design and manufacture of customized products is explored. A system’s encapsulated rules and models have to be updated and refined due to shifting prerequisite and both the system and the solutions generated for a single specification will change over time. These changes affect product management and the ability to meet legislation and customers’ requirements regarding documentation and traceability, as well as the company’s ability to provide services, maintenance and supply spare parts. This work addresses this challenge and introduces a concept with required functionality for capturing, structuring, searching, retrieving, viewing, and editing a system’s embedded information and knowledge. The concept has been developed and applied to a real case in collaboration with a company acting as a sub-supplier in the automotive industry. The objective was to enable and facilitate maintenance and updating of existing system and support the reuse of functions and system encapsulated generic design descriptions in the development of future systems.