Researchers developed a theory-based digital health platform called Empower My Congenital Heart (EMCH) through interviews with 54 participants and engagement with 21 community partners from advocacy organizations. The intervention targets the COM-B behavioral framework—addressing capability, opportunity, and motivation barriers that prevent adults with congenital heart disease from maintaining lifelong specialized care. The platform includes educational modules, peer support networks, appointment planning tools, and digital medical passports accessible via web and mobile devices. This research addresses a critical healthcare gap, as adults with congenital heart disease frequently lose connection to specialized care, leading to preventable complications and premature death. The community co-design approach represents a promising methodology for developing patient-centered digital health tools, emphasizing accessibility, credibility, and scalability while centering patient voices and experiences. However, this preprint describes only the intervention design phase—actual effectiveness data from implementation studies are still pending. The theoretical framework provides a solid foundation, but real-world outcomes including patient engagement, care continuity improvements, and clinical benefits await peer review and validation through controlled trials.