finder

• cmd-shift-. show/hide hidden files

plugins

• brew cask install qlstephen quicklook unknown file extensions as plain text
• brew cask install qlcolorcode quicklook source code
• brew cask install qlmarkdown
• brew cask install qlimagesize

jetbrains

• ctrl-shift-j join lines`

xcode

get old version from https://developer.apple.com/download/more/