Double-Tap to Wake is a pretty useful feature found on some phones and it is surprising it hasn’t become a default feature for Android.
The opposite of double-tap to wake is Double-Tap to Lock and even fewer devices with the first feature have the second. OnePlus phones have Double-Tap to Wake but the gesture doesn’t work for locking the phone until now.
In the latest beta update released for the OnePlus 5 and OnePlus 5T, one of the new features included is Double Tap to Lock. Once you get the update, you can activate it under phone settings and a double-tap on the homescreen should lock your device.
OnePlus has also improved the search history for the app drawer and optimized scanning logic for large files when you use the file manager.
The new features should be bundled with a stable update in future.