Actions marked as storable can be seen in the Storage tab. Storable actions are automatically configured in Lightning Experience and the Salesforce mobile application. To use storable actions in a standalone app (the .app resource), you must configure client-side storage for cached action responses.
Read more about client-side storage here: https://developer.Salesforce.com/docs/atlas.en-us.Lightning.meta/Lightning/controllers_server_storable_enable.htm.