How add new page in my integrated Shopify app UI which is already published on Shopify App store.

[neomi-dov]

My app is already approved by Shopify and available on Shopify App store with unlisted label. No, I want to add few more features on this app, my new features are within the scope and required to use Shopify Billing API for app monthly subscription payment. The current published app is free to install and the second version is paid. I want perform two actions:
1. Change the app visibility from unlisted to Listed so that it available on search
2. Publish additional features that I developed which required to use Shopify Billing API for Usage fee and monthly subscriptions fee.

I want to know how to submit this additional feature to Shopify Support for review and approval as it's an upgrade to my existing app. I don't see any option to submit again.
Also I want to know if update my codebase with new features for my existing app then it will also reflect on existing app Ui so how it will be handled without approval?

Actually I am totally confuse how to update my code base with new features, 

Thanks in advance.