https://wccftech.com/beta-5-of-macos-10-14-5-watchos-5-2-1-and-tvos-12-3-now-available/

Apart from iOS 12.3 beta 5, Apple has released the fifth betas of macOS 10.14.5, watchOS 5.2.1 and tvOS 12.3 as well.

Apple has refreshed its entire beta lineup right now and you can go right ahead and download it all. Starting with macOS 10.14.5 Mojave beta 5, you can download the latest software update straight from System Preferences > Software Updates. Make sure you are connected to WiFi and have saved all your work before proceeding as the installation requires you to restart your Mac.