@Moira Thank you so much for this advice! What package.json should I change the build scripts in since we are working specifically with a UI Extension?
Also, are you sure that I can change the build command for a UI Extension? Here (https://shopify.dev/docs/apps/tools/cli/structure#build-and-deploy-process) it says that it builds extensions with ESBuild, and I’m not sure how to alter the config of the build process to include the addition of CSS files.