If you want to be able to end the current session of Ubuntu or even shut down / restart your PC rapidly from Dash instead of having to click around various menu, you have to install “power-commands”.
To do it, first enable the “atareao” repository:
sudo add-apt-repository ppa:atareao/atareao
sudo apt-get update
And then install “power-commands”:
sudo apt-get install power-commands
Once done it, you have various new commands to manage your session directly from Dash