Google really needs to overhaul the Pixel's Now Playing capability. Until then, Now Playing history has lost its "Favorites" tab.
With the latest Android System Intelligence update (which powers Now Playing), the bottom bar has disappeared. There's just the reverse-chronological "History" feed, with no second tab.
This is presumably a bug as the underlying capability remains available. There's still a heart next to each song, while you can favorite from the lockscreen or notification.
This is an issue with version B.13 of Android System Intelligence, which is now widely rolling out.
The app needs to be completely overhauled with Material 3 Expressive after skipping Material You entirely. Now Playing history frustratingly still doesn't transfer over when you get a new Pixel phone. The last big update (at the end of 2024) was "Enhance Now Playing" that introduced album artwork.