VS Code has been making progress to support Jupyter notebooks (https://code.visualstudio.com/docs/python/jupyter-support), but it's not quite there yet. Code completion works, but other features such as user snippets are missing, and it can be quite laggy. Apparently that's because the VS Code team has to reimplement a lot of stuff for Jupyter specifically (compared to adding support for Rust or Go with a language server).
Another great local-first wiki tool is Obsidian (https://obsidian.md/). Each page is just a markdown file in a dedicated folder. They have backlinks and a bunch of plugins.
Thank you, I somehow missed that link. For reference: the crossbones refer to the "xxx" in the name of the original server (xxx.lanl. gov). The smiley and the green background don't seem to have any specific meaning though.