In hindsight, it was a curious omission, but when Google debuted the diagonal swipe gesture to trigger the Assistant in Android Q/10, the only way to disable it was to change navigation modes or just straight-up disable the Assistant as your assistance app. Now, as of Android 12 Beta 3, it's something you can separately disable if you'd like to.

In case you are unfamiliar or choose to lead a gesture-free life, Android's somewhat recent and iOS-inspired gesture navigation system also adds a corner gesture to trigger the Google Assistant — handy, given you can't long-press a home button that isn't there. Swipe inward anywhere around a 45-degree angle from the corner, and it's triggered, activating the Assistant easily. And it's not just on Pixels; most recent Android phones have the feature if you enable the non-button gesture navigation.

Left: Beta 2. Right: Beta 3. 

The new toggle lives in the deeply nested Gesture settings sub-menu (Settings -> System -> Gestures -> System navigation -> the cog next to gesture navigation) and does exactly what you expect. Tap it off, and poof, the corner-in gesture is no more. If you try the maneuver while the feature is disabled, it gets picked up as the app-switching gesture instead.

While it's nice that Google added the option, the fact that it wasn't something folks were crying out about to begin with is also a little curious. After all, it has essentially been forcibly enabled when the Assistant is set as your "Assist" app while gesture navigation is turned on until now. The only way before to turn it off without mucking around with root or ADB was to outright disable one of those two things  But going forward, now you'll have the choice for whether to use the corner trigger or not — if, for example, you like Android 12's new iPhone-like power button shortcut better and don't want two actions for the same thing.