In a post on its developer blog, Apple says that new Design Resources include a full set of “essential” AppKit UI [user interface] elements for designing Mac apps in Sketch or Photoshop.
“It’s never been easier to design apps for Mac and Apple Watch,” Apple says. “The Human Interface Guidelines now include a full set of essential AppKit UI elements for designing Mac apps in Sketch or Photoshop, as well as dozens of new UI elements for watchOS apps, watch face templates for designing complications, a color guide, and new text styles.”