SF Symbols provides a set of over 2,400 consistent, highly configurable symbols you can use in your app. Apple designed SF Symbols to integrate seamlessly with the San Francisco system font, so the symbols automatically ensure optical vertical alignment with text in all weights and sizes.
https://developer.apple.com/design/human-interface-guidelines/sf-symbols/overview/
As far as I can see, macOS does not support NSImage(systemName: String) syntax when trying to use SF Symbols in a macOS project.
To be specific, I was trying to use an SF Symbol glyph on a toolbar item.
SF Symbol are now available with macOS 11.
SF Symbols are available in iOS 13 and later, macOS 11 and later, watchOS 6 and later, and tvOS 13 and later.
Here is how you use it:
NSImage(systemSymbolName: "hammer", accessibilityDescription: nil)
If you want to support macOS 10.15 and below you have to use the SF Symbols Mac app and export the symbol as SVG and import it back to an asset file in your Xcode project. You can get the app from here.