I am generally very pleased with Dorico 4 and all the possible individual adjustmentsI can make.
But I wasn’t pleased when I had done the layout of my first guitar book and then decided to add a front page before the first music page. This changes all layout actions and images in the score. Such a simple action shouldn’t have these major consequences.
Also moving a frame (text or image) by using alt+arrow has been the cause of Dorico shutting down.(a few times already).
Depending on which layout options you mean, there might be possibilties to prevent that from happening, but in general you are right, that Dorico is not very forgiving, when doing major changes like adding pages after having done the detail-work.
We discussed this issue in this topic, especially the idea, of adding a way to “lock” the design, but this does not seem to be the plan.
This was basically the best answer I got: Don’t do things like additional layout pages in Dorico itself.