You can use the env var BABEL_SHOW_CONFIG_FOR
to print the effective config for a file. This is useful in cases like a monorepo, where the babel config extends from a root config.
Note that you have to point to a file, not a directory, e.g.
BABEL_SHOW_CONFIG_FOR=./src/myComponent.jsx npm start
https://babeljs.io/docs/en/configuration#print-effective-configs