it’s possible to enable some hidden features for the ‘Twitter For Mac’ application with some Terminal commands. With the following command you can enable to close the ‘New Tweet’ window with the ESC-key. Close Twitter and add the following command in Terminal.
defaults write com.twitter.twitter-mac ESCClosesComposeWindow -bool true
Restore the default setting:
defaults write com.twitter.twitter-mac ESCClosesComposeWindow -bool false