The problem

Cocalc exports notebooks to LaTeX using a default provided by nbconvert when File > PDF via LaTeX is clicked in the menu.

I wanted to be able to customize the default LaTeX settings (found at /ext/jupyter/nbconvert/templates/latex), however this contains read-only files on the system. So, I created a local config, but they do not automatically override the system settings. After interpreting the docs, I found how to override the system default.

The recipe

1. First, copy the folder /ext/jupyter/nbconvert/templates/latex to /home/user/.local/share/jupyter/nbconvert/templates/latex.

mkdir -p /home/user/.local/share/jupyter/nbconvert/templates/
cp -r /ext/jupyter/nbconvert/templates/latex /home/user/.local/share/jupyter/nbconvert/templates/

2. Create a config file at .jupyter/jupyter_nbconvert_config.json with the following contents:

  "version": 1,
  "Exporter": {
    "template_path": [
      "/home/user/.local/share/jupyter",
      "/home/user/.nbconvert",
      "."
    ],
    "template_paths": ["/home/user/.local/share/jupyter/nbconvert/templates/latex"],
    "preprocessors": [
      "jupyter_contrib_nbextensions.nbconvert_support.CodeFoldingPreprocessor",
      "jupyter_contrib_nbextensions.nbconvert_support.PyMarkdownPreprocessor"
    ]
  }
}

The result

Now you will be able to edit the config files for LaTeX documents in /home/user/.local/share/jupyter/nbconvert/templates/latex and the cocalc system will use those settings when you click File > PDF via LaTeX. It also appears that defaults for other export types are not broken by this process, only the LaTeX export is changed.