I think for a better answer to your question it helps if you first break it categories (juniper, pine, deciduous?) and stages of development.
I liked Bonsaify.com for Eric’s juniper and Japanese Black Pine (JBP) courses on development. Bonsai Tonight’s blog on JBP is great for seeing stages and steps of development. But also for pruning techniques to ramify and develop pads.
Mirai’s premium content is wealth of information, but I haven’t ventured into the new courses to know if you could answer specific questions. The original content had video(s) on apex creation, his design principles relating trunk/primary branch/apex movement, and numerous videos of him making pruning and wiring decisions during the video.
But there is no substitute for actually getting to see bonsai trees in person and taking the time to study them. Visually work through how the trunk line and branches were formed and selected. The spacing and negative space.
Even after +15yrs, it is still the hardest aspect for me to put into practice.
Edit:
@Gabler beat me to it with a more succinct and spot on recommendation!