[Solved]-Where is the documentation for jssPreset in this CodeSandbox? I didn't find it-Reactjs

I don't believe there is currently any documentation specifically on jssPreset, though the JSS plugins documentation shows an example of using it.

When something isn't explicitly documented, the next place to look is the source code. Looking at the jssPreset source code, you'll find that this returns a JSS configuration object that includes all the JSS plugins used by Material-UI.

If you look for usages of it, you'll find it used to create the default JSS instance.

The sandbox you linked to contains the following code:

import jssTemplate from 'jss-plugin-template';

const jss = create({
  plugins: [jssTemplate(), ...jssPreset().plugins],
});

function StringTemplates() {
  return (
    <StylesProvider jss={jss}>
      <Child />
    </StylesProvider>
  );
}

This is using jssPreset to get the default set of plugins included in Material-UI, and then adding one more plugin to the list (jssTemplate), then specifying to use that new JSS configuration via StylesProvider.

You can find the list of available JSS plugins in the JSS documentation: https://cssinjs.org/plugins?v=v10.0.0#jss-plugins.