3D Touch multitasking returns to iPhones in the iOS 11.1 beta 2 release. First introduced in iOS 9, it let users with certain iPhone models switch apps without the home button. The iPhone 6s and later models have a haptic component that enables 3D Touch.
Haptic App Switcher
3D Touch multitasking was removed during the iOS 11.0 betas. It wasn’t added back when the official release came out, with Craig Federighi adding:
We regretfully had to temporarily drop support for this gesture due to a technical constraint. We will be bringing it back in an upcoming iOS 11.x update.
Thanks (and sorry for the inconvenience)!
Other features coming in iOS 11.1 include new emoji and (possibly) Apple Pay Cash and iCloud sync for iMessages. iOS 11.1 beta 2 is out now for developers.