Train managers face a challenging work environment, characterized by a heightened risk of passenger aggression within spatially confined environments. Further, the rarity of threatening incidents makes skill development difficult. This paper presents the design and development of a Virtual Reality (VR) training artifact aimed at equipping train managers with de-escalation skills through immersive VR simulation of threatening onboard scenarios. Developed in collaboration between SJ (Sweden's largest train operator), University West, and VR developer Tenstar, the project operationalizes Design Thinking (DT) as the micro-level method within an Action Design Research (ADR) framework. Two Minimum Viable Products (MVPs) were developed as boundary objects to surface tacit practitioner knowledge and validate scenarios before committing to costly VR development. A modular JSON-based architecture decouples scenario content from the VR implementation, enabling rapid iterations without modifying the underlying VR environment. Evaluation indicates strong perceived utility and confirms that the design process successfully captured the complexity of real onboard work practices. The paper contributes a methodological approach for developing VR training artifacts in complex, practice-embedded contexts.