Power Suite Ubuntu x86/OS Enhancement Utility/Notification
From ESS-WIKI
Brief
You can toggle the system notification feature of Ubuntu ON/OFF by clicking the "Stop System Notifications" button.
Steps
Step1. Select the “OS Enhancement Utility” page.
Step2. Click on "Stop System Notification" switch button.
Step3. Click on "Confirm" to change the settings.
Result
Checking the message notification bar at the top of the Ubuntu desktop, you will find that "Do Not Disturb" has been turned on.