To make your daily interaction and working with your Shopify E-Commerce store fruitful and productive, you can deploy/install a Shopify private app, which can be accessed within the Shopify private store only.
Shopify private apps, as you are already aware, is not publicly listed and have a specific role in your E-Commerce Shopify store. Whether it is seo, analytics, inventory management or any other line of business that your E-Commerce store needs to link with - a custom app can always be built using Shopify private application development.