Managing native configuration with Drupal 8 makes it very easy to make changes or additions to the configuration from a site instance (such as a development environment) to another site instance (the production environment). These configuration exports and imports of a site are made in one piece: that is, the entire configuration of a site, which is updated. Thus if configuration additions have been made to the production site, they will be overwritten at the next import of the configuration if these configurations are not present also on the source environment.
But there are valid use cases where certain configurations can and must be modified directly in production. Examples of immediate use are, for example, the creation of new Webform forms, or the creation or update of new Newsletters managed with the SimpleNews module. It is quite legitimate for a webmaster to modify or create new NewsLetters on the production site. It's almost like content, except that ... it's a configuration entity.
Let's discover how to manage these particular cases with the module Configuration split, module that will allow us to maintain an organized process to manage the evolution and maintenance of a site in production while allowing the modification of some configurations live.