I don't know recent Samsungs, but most phones these days let you customise which shortcuts appear there. Do you have anything that might be an "edit" icon when you pull the notifications down? It's a little pencil in vanilla Android, but Samsung change everything they can so it might be something different for you.

 

Here's where it is on my phone (Pixel 2).

 

Yes recent Samsung products such as my tablet does include an edit mode.

 

Swipe down further. Also you'll see here on the Quick Settings screen with two dots above the brightness slider that there's another page on the right.

Is it definitely not there?
Try something similar to Network and Internet Settings - Airplane Mode.

 

Settings - Connections - Flight Mode