To add a Stack to your OS X Dock that contains the most recently used Applications, open a Terminal and enter the following line of text:
defaults write com.apple.dock persistent-others -array-add '{ "tile-data" = { "list-type" = 1; }; "tile-type" = "recents-tile"; }'
And then type:
killall Dock

Your dock will now have a new Stack. Give it a click.

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