Maybe these are not new, and are commonly known, but for the new on OSX86
Make the Safari Debug Menu appear:
Quit Safari then in Terminal type
defaults write com.apple.Safari IncludeDebugMenu 1
Make any App Icon Transparent in Dock when it is hidden
In Terminal type defaults write com.apple.dock showhidden -bool true
then type killall Dock
I like the second one!
Is there a way to undo it?