The fourth beta of macOS 10.12.6 has now been seeded to developers. This comes a little less than a week after the last seed. We’re unsure what’s new in this version. It likely brings bug fixes and other improvements.
To get this version developers can go to the Mac App Store > Updates > Software updates > macOS 10.12.6 beta 4. If you’re not on the beta yet you can download the installer from the developer center.