Introduced Gallery View, allowing users to browse files visually, along with enhanced metadata in the preview pane.
Early beta users reported issues with the App Store, sometimes requiring users to sign out and back in. macOS Mojave 10.14.b1 (18A293u)
As of November 2021, macOS 10.14 Mojave is unsupported and does not receive security updates. Introduced Gallery View, allowing users to browse files
Based on your query, 14.b1 (Build 18A293u) , which was released in June 2018. Key Features of Mojave 10.14 Beta (18A293u) Introduced Gallery View
A new, more robust screenshot utility (similar to iOS) with on-screen tools.