You've seen how easy it is to add CSS to your Awesome Table template (within Google Sheets). An alternative to this is adding a custom CSS file. You can also use this method to add an external CSS library (like Materializecss or Pure.CSS for example).
For this exemple, we are going to use an external CSS file hosted in GitHub Pages.
1. Copy the direct CSS url generated once the CSS file is uploaded (or created in GitHub). In our example, the direct CSS url is: https://darny.github.io/csstemplate/style.css.
2. Go to the Awesome Table sidebar menu, click Formatting.
3. Then paste your direct url link in the Custom CSS url field.
4. Finally, click Update app.
Screencast covering steps 2 - 4.