In the Strings section of the Core Topics/Resources page it says:
scope |
No | See resource scopes. String can have the additional setting scope which removes it from the runtime. This is useful when a string is only used within your setting definitions. |
But "setting" should actually be "settings". If you try to use "setting" the compiler tells you its an invalid scope, but doesn't list the valid ones, making it hard to guess what the correct spelling is.
Also, this feature deserves a lot more coverage. It's really valuable (thank you for adding it!), and deserves to be seen (and explained in more detail than this one throwaway remark buried in a table).