Valve have rolled out an update for the Steam Deck Beta and Preview channels, which includes new features that are still being tested. You can opt into this in Settings > System > Steam Update Channel.
From the official changelog:
- Added ability to adjust image display settings for external displays that have overscan issues
- Fixed issues with some images being too large when viewing guides in the overlay
- Fixed spoiler tags in guides to be selectable so that they can be revealed
- Fixed issue with medium length game names in the Main Menu Overlay not properly scrolling
- Fixed Achievements page not updating properly when a new achievement was earned