there is no TOC
There is the overall TOC is on the left side, and the TOC for the current page is on the right. Note that one of or even both TOC can be hidden if your browser window is too narrow.
or followable links eg line() command
There are no links in the code blocks, but I don’t think that should be changed.
Often even mentions of functions or classes are not linked to their documentation page - that’s an issue, I agree. Pull requests are always welcome! Or even issues on GitHub if you want for a particular place in the documentation to link to some particular page.