When iOS updates, various features will be added, but not all of them will be available immediately. As of October 2019, the question "Quick Path" is supported by software keyboards in 7 languages such as English and French, and Japanese (numeric keypad) is not applicable.
QuickPath is a new feature of the software keyboard that allows you to enter characters by tracing the keyboard. If you trace the keys on the screen in order, the word will be input while performing predictive conversion.
To take advantage of that feature, switch to a software keyboard in a language that supports QuickPath, such as English. If the input mode of the software keyboard is Japanese, tap the globe button at the bottom left of the screen and select "English (Japan)".
Using QuickPath is intuitive. For example, when typing "iphone", first place your finger on the "i" and then slide your fingertip to the "p". Next, by the time you start sliding your fingertip in the direction of "h", the candidate "iphone" should be displayed in the area where conversion candidates are displayed on the software keyboard, so slide your fingertip toward it this time. Let me. Since it is not necessary to tap all the characters that make up the "iphone", the input speed is greatly increased.
You can tell if QuickPath is working with an animated effect similar to an airplane wake on your software keyboard. QuickPath can be disabled by opening the screen in the order of "Settings" → "General" → "Keyboard" and turning off the "Trace input" switch.