If you are referring to the ability to move your finger from one key to another without lifting it, then it's called swiping. The Swiftkey keyboard app has had that feature for a very long time (I had it on a Samsung Galaxy S2) and I think that app is the main keyboard app installed by most users on Android devices.But a bigger omission is 3D Touch, I use it daily on iPhones to turn the keyboard into effectively a touchpad to move the cursor like a mouse when typing, I still can’t believe most Android devices don’t have this yet as this has been on iPhones since the 6S!