But there is another way, you can edit the menu's using a program called "alacarte".
It's installed by default (on my installation) but not present in the menu's (how convenient...)
So, open a command prompt (ALT+F2) and type "alacarte"
When the application opens, go to the "System Tools" section and add a new item, just like the screenshot and close alacarte. (The YaST icon is located at /usr/share/icons/hicolor/48x48/apps/yast.png
Now you should see the YaST icon when openening the dock