Is there anyway for me to use this extension on JupyterLab. GitHub - alwaysmpe/jupyterlab-custom-css: Add custom CSS rules for JupyterLab (It has been modified from the one available by jupyter labextension …)
In its current state… maybe? How willing are you to do custom work and/or maintain it for your purposes?
If you want a pip- or conda-installable custom style tool compatible with JupyterLab 3, there is also (disclaimer: maintainer) GitHub - deathbeds/jupyterlab-fonts: Data-driven Style and Typography for JupyterLab powered by JSS. (previous thread). It offers settings and notebook-based style customizations. It’s powered by jss which allows for tricky things like font faces (hence the name), media queries and nested selectors.