Modules such as Config Split want to modify the configuration when it is synchronized between the database and the exported yaml files.
This module provides the API to do so but does not influence a sites operation.

How it works

Configuration Filter swaps the service from Drupal 8 core.
The new service wraps the file storage and applies filters to it.
This allows other modules to change the configuration as it gets imported or exported both in the Drupal UI and with drush. (drupal console patch pending)

Supporting organizations: 

Project information