Modify custom module's setting.yml without reinstalling I have made a simple custom module in Drupal 8, in which I use a settings file (config/install/my_module.settings.yml)

I have one entry, let's say 

module:
  key: 'qsdqsd'


So when I install the module, I can use this entry in my controllers. 
But if I need to modify anything in this file (adding an entry, for instance...) I can't use it in my controllers (config->get(module.new_entry) returns NULL) unless I uninstall then reinstall the module.

drush cache-rebuild did not help neither.

What am I missing?
You can try the module config_sync, there you can update the site's configuration from your custom module.

afaik there is no official way to update configuration from an updated module.