The big new feature is per app time limits. Now parents can set time limits for individuals apps on their child's device, letting them restrict games or video apps while allowing access to educational resources or communication apps, for example.
Another feature which kids will appreciate is bonus time. Parents can use the Family Link dashboard to grant extra time for their child to finish what they're working on or finish the level of a game, which is a way to compromise with kids who ask for the universal "just five more minutes".
Finally, Family Link is now more easily accessible. It can be found in device settings in Android 10, under "Digital wellbeing and parental controls".