thank you for writing up this detailed feedback!! the left nav interactions and scrolling is definitely something we want to fix soon, it's a very frustrating experience!
for the reference api docs id encourage you to head directly to pulumi.com/registry instead of by way of the docs. you can find a link to this on the very top right of the website.
we are also overhauling the docs landing page to make it easier to quickly get to the registry.