Android 8.0 Oreo added the ability to snooze specific notifications, so they re-appear after a set amount of time (15 minutes, 30 minutes, or an hour). This is currently activated by partially swiping a notification to the left or right, but in Android Q, the snooze function is taking over the swipe left gesture.

In the Android Q beta, swiping left on a notification only shows the snooze and block controls. If you want to completely dismiss an alert, you now have to swipe right. This will probably take a while to get used to, assuming it sticks around for the final release.