In a 100-Day-Challenge, French and German product teams joined forces to co-develop a note-taking application for integration into their respective public sector office & collaboration suites, openDesk and La Suite Numérique. We show how this feature was developed, highlighting the challenges and successes of our joint endeavor. We'll explore the design and technical decisions behind the application and how it enables collaboration across different national workspaces. By sharing our experiences and lessons learned, we aim to showcase the potential of joint European initiatives in shaping sovereign digital workspaces that transcend borders.