how to configure drupal settings to be available to visualize the available variables?
You can use kint which will print you all the variables
https://www.webwash.net/how-to-print-variables-using-kint-in-drupal-8/
or dpm (in devel module)
https://www.drupal.org/docs/contributed-modules/devel/dpm-and-other-devel-functions