Tabletop exercises (TTXs) are used to train managers and other actors to deal with emergencies. These exercises that focus on the organisational coordination are planned and controlled by exercise managers through scenarios with predetermined events that participants discuss and act upon. Such exercises may lead to actors being ill prepared to deal with dynamic and emergent situations and problems. To address this knowledge gap, we apply an action design research approach to develop a TTX structured around non-sequential themes instead of predetermined events, thus allowing the participants to identify their own problems during the exercise. Our research contributes to existing knowledge by developing a set of design principles.