So far, there hasn't been documentation on how to change the background color of the canvas with storybook toolbar theming controls. The storybook-dark-mode branch of this repo uses the storybook-dark-mode package to demo this.
Make sure to add the package to addons in .storybook/main.js and
take a look at .storybook/preview.tsx to see the code.
This library was bootstrapped with TSDX.
After cloning the repo, run npm run install. Then run npm run storybook.