The DIAMOND project undertakes a transdisciplinary (TD) approach to update, expand, open, and develop scenarios for six Integrated Assessment Models, with the aim of addressing net zero emissions and sustainable development. WP2: Codesign leads this TD approach, which is broken down into three multi-stage phases: i) mutual understanding; ii) knowledge co-production; and iii) model co-ownership. Deliverable D2.4 presents the results of the first two out of three stages in “Phase 1: Toward Mutual Understanding”, which is based on the concept of “joint-problem framing” indicated by the TD scientific literature as the initial step within a fruitful stakeholder engagement plan. The aim and output of this phase is a set of stakeholder-informed research questions, which are co-created in three stages. Stage 1 is a familiarisation stage, aiming to find common ground among DIAMOND partners and their work. Stage 2 focuses on reaching mutual understanding of the goals and aims of the transdisciplinary approach to be implemented by DIAMOND partners. This Deliverable, D2.4, presents these two stages and concludes in actions falling under three themes. These themes include: (a) strengthening internal and external communities of practice, (b) focusing codesign activities, and (c) improving the effectiveness of stakeholder engagement. These outcomes will be picked up on in Stage 3, which commenced in January 2024 and will conclude Phase 1 of DIAMOND’s codesign process with the output of a final set of stakeholder-informed research questions, to be presented in Deliverable D2.5 (update of this deliverable).