Sustainability transformations involve wicked issues characterised by an absence of definite problem framings or solutions. Engineers play a crucial role in addressing such situations. However, engineers often lack the emotional capabilities to navigate open-ended and complex issues adequately. In this paper, we focus on the emotional challenges in engineering students' learning on wicked sustainability issues. We explore how emotional scaffolding can support engineering students in co-creating new ways of handling wickedness via expansive learning. Using a combination of narrative description and systematic mapping of emotional interactions, we analysed video data from student group work on wicked sustainability issues. We identified seven types of educational challenges that triggered expression of a wide range of emotions, and observed diversity in how enacted emotions hindered or enabled learning. We concluded that emotional scaffolding must be viewed as a system, and educators should focus on creating favourable emotional learning environments rather than attempting to micromanage students' emotions through generic interventions. To support in navigating the complexities of emotional scaffolding for sustainability learning, we propose a classification of scaffolding intents building on leverage point thinking. It ranges from shallow adjustments to learning environments to deeper transformations of the emotional logic underpinning teaching and learning.