How can I avoid saved configuration settings to be exported? I have a custom module and I added a form that allows the administrator to save some settings. Now, when I export the configuration (drush cex), I notice that these settings are being exported to a file (mymodule.settings.yml in the config directory).

I don't want to export these settings. How can I avoid it?
If you don't want to export configuration you should use State API.
From documentation:


  
  It is specific to an individual environment.
  You will never want to deploy it between environments.
  You can reset a system, losing all state. Its configuration remains.