I think we have a little confusion on how to attach scripts to quests, and I fear Khajiit is going to run away screaming.

The thing is, Renee and I are describing two different ways to attach a script to a quest. So I'll try to sort it out.
Method 1 - create the script from the Quest window. This is what Renee is saying. When you open the Quest window and click your quest (or make a new quest and click it), you can attach a script to it. But what if you haven't made that script yet? Well, then you can click the three dots near the "Script" drop-down box and it will take you to the script editor where you can enter and save your script. Then you return to your Quest Window but your script is not in the list...

because it hasn't caught up with you yet. I find that you actually have to click another quest first, then come back to your original one, and then your script will be in the list.
For this reason I do it differently.
Method 2 - create the script first. In the CS there's an icon with a pen on it - that's the script editor. You can also open it from the menus. Click it, and select "New script". Copy-paste the script above (or write your own, hehe), and save. Make sure that the script type is set to "Quest" rather than "Object" (it is "Object" by default). In the standard CS this drop-down is on the bottom of the window, but in the CSE it's on the top.
Now open your Quest window, go to your quest and you will find your script in the drop-down box. If it isn't there, then you didn't make it a Quest script.
Once you set the script to your quest (or do any other thing, like give your quest a name or something), make sure to click another quest or at least one of the other tabs of the same quest. THIS IS WHEN YOUR DATA GETS SAVED!!! If you close the window without doing this, you may find that your changes weren't saved!

This is a problem that I encountered on every tab!! You think you've done something, you're sure you weren't drunk, but you go back in and it's not there! So I now have a rule to always click on another quest before exiting.
But it isn't all that complicated, really. It's a bit scary at first, but you soon get the hang of it.