The Extended MathJax plugin enhances the math rendering capabilities in Obsidian by allowing users to load a custom MathJax preamble file at startup. This enables the use of additional MathJax extensions, such as `mhchem` and `bussproofs`, which can be particularly useful for scientists, researchers, and students who need to typeset complex mathematical equations. The plugin also provides an easy way to define custom macros in a `preamble.sty` file located in the root of the vault. With this plugin, users can create a personalized math rendering experience tailored to their specific needs.