Health researchers increasingly work with patients in a participatory fashion. Active patient involvement throughout the research process can provide epistemic justice to patients who have often only had an informant role in traditional health research. This study aims to conduct participatory research on patient experiences to create a solid research agenda with patients and discuss it with relevant stakeholders. We followed a participatory research design in 18 sub-studies, including interviews and group sessions (n = 404 patients), and dialogue sessions (n = 367 professionals and directors in healthcare and social work, municipality civil servants, and funding agencies) on patient experiences with psychiatric care, community care, daycare, public health, and social work. Findings from the eight-year study show that four priorities stood out: attention for misuse of power and abuse; meaningful participation; non-human assistance, and peer support. Moreover, that: (1) patients, based on their experiences, prioritize different topics than experts; (2) most topics are trans-diagnostic and point to the value of a cross-disability approach; and (3) the priorities of patients are all too easily dismissed and require ethics work to prevent epistemic injustice. Long-term investment in a transdisciplinary community of practice offers a solid basis for addressing patient-centered topics and may impact the quality of life of people living with chronic illness, disability, or vulnerability.