Button to turn on Do Not Disturb
The Do not Disturb setting is easily accessible in the notification panel on most Android devices.

To find it on a Galaxy S9+, using two fingers, swipe from the top of the screen, and you'll see all available quick settings. You should see DND mode as one of the option. (If it's not there, swipe the screen to the right or to the left to find it)

Tap on the DND setting to turn it on or off. Long press on it to enter more DND settings.

Below, is a screenshot of how this looks on a galaxy S8. it looks similar On an S9+


How to move it to a more convenient place:

To move the quick setting to a more convenient place like next to the WiFi setting, all you have to do, is press on the three dots (circled with green in the screenshot) and press on button order this will give you access to changing the order of the settings.