Once and forever, this is the final and correct information to view the hidden /Library folder from the Mac OS. We open the Terminal /Applications/Utilities/Terminal. Don't worry, the terminal will not bite and the command ist really only to make the invisible folder visible.
Unhide the Mac OS LibraryFolder
To make the Library folder visible, copy this code in the terminal window and hit enter
chflags nohidden ~/Library/
The Library folder is now visible.
To hide the Mac OS Library Folder
If you want to hide the folder, use this command:
chflags hidden ~/Library/
That's it. The Library folder is invisible now.