True, the way they handled this in Sierra is that this can be set up per chart, so only specific charts inherit lines from other specific chart(s). Could be either one way or two way sync. So it doesn't force it across every single open chart for that symbol. At the end of the day if someone sets up 100 charts to all be in sync on drawings originating from any chart they'll need to understand the implications/limitations involved in this. Anyway I leave these architecture considerations to someone like you who is far more experienced in this than me 🙂