Hello Toad,
That's not my question, i know that iDVD has the loop feature (btw, thanks for this quick tuto 🙂 )
The real question is: iDVD for Sierra (or High Sierra) doesn't really exist, and I didn't succeed in installing it, following your tutorial on another post on apple community. That's why my question was about this: which alternative for iDVD in high sierra or Sierra?
By the way, I find my answer: Wondershare DVD Creator does it very simply (but kinda expensive: 50$), there's also DVD Creator Pro in the app store, for 10,99€.