All the relevant comments are over there https://bugs.python.org/issue28044 which got closed as soon as I added my comment, which isn't a particularly friendly sequence of events. If the issues there are outdated, they should be marked outdated and transferred here as part of the transition.

My comment is that the sidebar menus scroll off the top when you scroll down the page, so they are pretty useless, instead of helpful.

Nice implementation of sticky sidebar.
https://css-tricks.com/sticky-smooth-active-nav/#more-273952

I haven't looked at the patch, and don't know what R. David Murray doesn't like about how it works, but I find the Python sidebar extremely annoying because it scrolls off the top, and would rather it stayed around visible.