I don't know if this has been posted before:
You can learn a lot by researching how Larian accomplished things in the main campaign but loading it in the editor takes a long time.
It's much quicker to make a copy of the STORY files and view them in notepad ++.
Here are some instructions incase you're not familiar with the process.
1. Google and download Notepad ++ (It's free)
2. Go to the folder: C:\Program Files (x86)\Steam\SteamApps\common\Divinity - Original Sin\Data\Mods\Main\Story\RawFiles\Goals (I'm assuming you bought the game from Steam, if not go to where your game is installed and proceed.
3. Make a copy of all of the files and put them in a folder on your desktop or wherever you keep your mod tips. (This is to ensure you don't corrupt the originals.)
Now you are ready to learn. I've used this in a couple of ways:
1.You can simply open Notepad ++, open a story file from your folder, and begin puzzling out what the coder was trying to accomplish.
2. From the folder you can use windows search to find specific functions in the story which you want to learn about. Right click on any results and choose open in Notepad ++. You can now see how the coder used the function.
In either case you may have to take text you found and do a search on it from windows to follow the logic.
I plan to put these on my smartphone so I can review them on the go.