Despite growing awareness of the importance of incorporating integrated science, technology, engineering and mathematics (STEM) learning into K-12 education, formal classroom implementation still faces obstacles. Teachers lack the knowledge and skills, especially design-thinking competence, required to design an interdisciplinary STEM curriculum. The goal of this study was to investigate different scaffolding modes that may influence the design-thinking competence development of STEM teachers. Twenty-four preservice teachers participated in this study, which was carried out in an online STEM preservice teacher training environment. The participants were assigned to six groups of two cohorts. Each group designed a STEM learning module. To support their online design meetings, the three groups from the static scaffolding cohort (SSC) received pre-defined guiding questions, while the other three groups from the adaptive scaffolding cohort (ASC) received contingent scaffolding from a human tutor. The Log data on the participants' conversations in the design meetings were collected and analysed using the epistemic network analysis (ENA) approach. The results revealed that the SSC and ASC had divergent design-thinking development trajectories and established distinct design-thinking patterns. Conversation analysis of the two cohorts confirmed the findings of the ENA analysis and provided evidence that the two scaffolding modes can help address challenges to collaborative STEM learning design and cultivate design-thinking competence from different perspectives.