I understand what you are looking for. It won't be present until an app allows for it. It is provided for by an app developer that allows local storage in addition to cloud based storage.
Apple's iWork apps will get you you this feature. Garageband, Pages, Keynote, Numbers.
Once you create a document in these apps, you select it from the main app page called Recents. Click on the BROWSE folder on the bottom and you will now see a ON MY IPHONE folder with a folder named for the app.
To be clear though... only the app that created the local folder our any of the cloud folders can use it. The Files app is not Finder for iOS. You will not have access to the device's filesystem.