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How to show hidden files and folders in Finder

Cmd-Shift-. (dot) is a toggle that will show hidden files and folders until you shut the Finder window. To make them persist, open a Terminal and type defaults write com.apple.Finder AppleShowAllFiles true
killall Finder

To make the ~/Library/ folder easy to see, use the Cmd-Shift-. (dot) method and then drag that unhidden folder into the Finder sidebar. It will stay.

Source: www.macworld.co.uk/how-to/mac-software/show-hidden-files-mac-3520878/