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.