Google introduced new gesture-based navigation with Android Pie to replace the traditional three button layout which was available on older versions of Android. Other manufacturers implemented this gesture-based navigation in their UIs while a few others went ahead and designed their own gesture-based navigation. Manufacturers like Xiaomi and Huawei had a custom gesture-based navigation that required the user to swipe from the left or the right side of the screen to go back instead of tapping the traditional capacitive button. It seems that Google is experimenting with a similar kind of gesture on the upcoming Android Q version.
These gestures were first spotted by XDA Senior member paphonb and covered by XDA Developers. The member was able to capture these gestures by running the Android Q system image from the emulator in Android Studio. From the recorded video it is clear that you will need to swipe from the edge of the display which is similar to the one seen on newer iPhone models. In the video, it can be seen that you can swipe from either side of the display which shows an arrow pointing to the left. This confirms that this feature is meant to replace the back button.
This gesture is currently experimental and isn't directly functional. People at XDA developers have found that you will need another ADB command to make this swipe gesture functional. Since these gestures are currently in beta, it is hard to tell if these will make their way to the final build of Android Q. Currently swiping from the left side of the screen opens a hamburger menu which could interfere with this.
If you have a Google Pixel smartphone running Android Q beta, you can enable it by running the following ADB commands to activate it.
adb shell settings put global prototype_enabled 1
adb shell settings put global quickstepcontroller_edge_width_sensitivity 48
To get the swipe gesture to work, the following command needs to be executed.
adb shell settings put global quickstepcontroller_gesture_match_map 172233