I really like Algolia's API Reference documentation. They explain in details each options quite a clear way.
https://www.algolia.com/doc/api-reference/widgets/instantsearch/js/
They also have a guide section with different use cases.
Nextjs example folder in their Github is also such a good one. It helped me a lot to get started. I know you are using Codepen but perhaps having a single place with all the examples would be amazing.
https://github.com/vercel/next.js/tree/canary/examples
Stripe is also a really great one
https://stripe.com/docs/api/payment_methods
Perhaps the main thing is the navigation. In this page for example https://greensock.com/docs/v3/Plugins/ScrollTrigger
All the keys you can add inside a scrollTrigger object is not part of the left navigation. The other day I couldn't remember how you named 'scrub' or 'markers' and because it was not part of the left navigation, it took me some time to find it. I ended up watching again the video.
Lodash is also really useful. I always find the information very fast. https://lodash.com/docs/4.17.15
Also maybe something that could help having a faster and more delightful experience would be to remove the animations on the left navigation sidebar in the docs. It feels a bit clunky.
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For the list of tutorials, that's such a great idea. Perhaps having a voting system for people to choose what tutorial they want next would be great. For me, having multiple tutorials or code examples on react would be amazing. Perhaps few examples using ScrollTrigger in all its glory.