This formative paper reviews the recent expansion in online teacher education programmes for "Education for Sustainable Development" (ESD) in southern Africa. The research informs the design of resource-based learning. An activity systems approach and a preliminary mapping of the design features for online learning for ESD enabled us to tease out key pedagogical and design concerns related to the development of an online learning resource platform for teacher professional development. The proposed online resource is conceptualized as an open-source learning platform for student and in-service teachers to learn together in work with schematic models of the process for mediating the inclusion of ESD in subject teaching. A course-activated learning process is being framed around an online navigation tool for a question-led induction into the use of six key ESD lesson-planning tools. The tools are approached as mediating tools for teachers to utilize together towards ESD lesson planning that is more subject-based and better curriculum-activated.