How to show hidden files and folders in Finder?
I don't think you can set this for individual folders. To set it globally, so that Finder always shows hidden files, run Terminal and enter the following two commands:
defaults write com.apple.finder AppleShowAllFiles true
killall Finder

To switch back, do the same but substitute false for true.
This works all the way through macOS Catalina (and betas for Big Sur).