This paper aims to outline the development of adaptation strategies and HMI guidelines for a COntroller adaptive Digital Assistant (CODA) to support Air Traffic Controllers in their operational duties by dynamically managing their workload. The strategies and guidelines were constructed using relevant literature and interviews with operational experts. The interim results include areas of specific interest based on operational knowledge, fourteen adaptation strategies and fifteen HMI guidelines. These results will serve as input for subsequent mock-ups that consider technical factors as well, and ensure an effective and usable support to controllers. These interim results provide valuable insights for developing supportive tools in the highly regulated, safety-critical domain of ATC, contributing to the advancement of operational safety and efficiency.