If you've added content to text or picture frames that are master page objects, this edited content will be migrated by default when replacing your master page(s) with a new master page. These master pages are considered 'smart' as they allow you to retain valuable copy when replacing master pages—for example, in the case of an underlying creative master page rework that should not affect content.
Smart master page layouts affect where and how images and text are arranged on a page or spread. Master page objects can be arranged to fit a new layout when master page content is migrated, as shown below.
When a new master page replaces an already applied master page, and content has been added to picture frames and text frames inherited from the existing master, Affinity Publisher determines the best destination for each piece of content according to the following rules.