With HCI increasingly addressing complex societal challenges, transdisciplinarity emerges as a necessary extension of interdisciplinarity that involves the active integration of practitioners and stakeholders. In this paper, we propose Research Labs as a format to foster transdisciplinarity through discourse and reflection in HCI. They are organized as theme-driven, moderated sessions based on a consistent setup of modules, each following a distinct objective to provide both, continuity for enabling systematic reflection processes while also ensuring flexibility for participants to address individual topics, or needs. This concept was applied within eight sessions conducted over three years in the context of participatory design of socio-technical innovation for informal care. With familiarity and trust, dynamic adaptation mechanisms, and participatory elements, we identify preliminary learnings on how to strengthen transdisciplinarity within HCI processes. The paper outlines opportunities and limitations of the format and suggests directions for further development and application.