To preview math symbols, some fonts are needed, you can install them manually or let the extension install them automatically on first launch (Works only on Windows).
Unfortunatly, you also need to set your theme colors in the extension settings, because the extension can't access the theme colors directly. You can find the settings in File > Preferences > Settings > Extensions > Typst Math.
By default, the extension will use the monokai theme colors.
Math snippets, commands and keywords to simplify math writing
Math preview directly in the editor :
Render math symbols from :
When you edit a line containing math symbols, these symbols will be rendered as text (as in the first image) to allow you to edit them easily.
Colors: Select your theme colors.
RenderSymbolsOutsideMath: If set to true, the extension will render symbols everywhere in the document, not only in math equations.
RenderingMode: Choose if you want to render just simple symbols or complex equations too.
Installing fonts seems to work only on windows, recreate a clean font installation system