Previewed at WWDC, launching in the fall.
Apple Seeds First Beta of macOS High Sierra 10.13.6 to Developers
The new macOS High Sierra 10.13.6 beta can be downloaded through the Software Update mechanism in the Mac App Store with the proper profile installed.
We don't yet know what improvements the sixth update to macOS High Sierra will bring, but it likely focuses on bug fixes and performance improvements for issues that were not able to be addressed in macOS High Sierra 10.13.5.
We'll update this post if any new features or notable bug fixes are discovered in the new macOS 10.13.6 beta.
Work on macOS High Sierra is wrapping up, with Apple now shifting focus to the next-generation version of macOS, macOS 10.14, which will be unveiled next week at the Worldwide Developers Conference.