Larian Studios Forums Divinity: Original Sin 2 - The Modding Dungeon Divinity - Original Sin 2 - Modding Troubleshooting Some questions regarding the Dialog Editor

That is Osiris script, which you have to write in the story editor. The wiki has Osiris reference documentation, but you first may want to have a look at a couple of community tutorial videos like this one, and also at the community Osiris tutorial page.