The adoption of virtual learning environments (VLEs) in education has grown significantly due to their potential to enhance learning. Effective learning in VLEs depends on managing cognitive load and sustaining motivation, particularly for complex tasks like developing teachers' professional vision -- the ability to notice and interpret classroom events relevant to student learning. However, the interplay between specific scaffolds, cognitive load, and motivation in VLEs remains underexplored. This study uses a mixed-methods approach to examine the effects of video modeling and prompts on motivation and cognitive load among 104 pre-service teachers learning professional vision in a VLE. While scaffolds improved motivation, they had no direct effect on intrinsic, extraneous, or germane cognitive load. Specific scaffold usage strategies yielded insights: note-taking during video modeling reduced extraneous cognitive load, process-related prompt use lowered extraneous load and increased germane load, and content-related prompt use enhanced motivation. These findings emphasize the importance of well-designed scaffolds in fostering motivation and managing cognitive load. Future VLEs should integrate structured prompts and active engagement strategies, such as note-taking, to optimize learning outcomes and address the critical link between cognitive load and motivation.