The File Sharing feature for copying data between apps and the computer is still there but the new Files app in iOS 11 and later should be more flexible. You can use iCloud Drive, Dropbox or similar services to move content to and from the device. See Create and manage ringtones in iTunes for more on managing tones with iTunes 12.7 or later. Books and Tones can also be found in their respective folders in the media folder. Apps previously downloaded with iTunes can be found in the Mobile Applications folder inside your media folder should you need them. This can be used to copy apps, ePubs, iBooks, PDFs, and tones from your computer to your device. See the Manually add items from your computer section of Manually manage content on your iPhone, iPad, or iPod touch using iTunes - Apple Support for the control that remains. See Changes in the new iTunes - Apple Support for more detail.

The intention is clearly that organization of these will generally take place on the device in future. Management of apps, books, and tones has been removed from iTunes 12.7.

Itunes 12.7 download to computer