Message: This page has a Theme Builder layout assigned

This article describes the following warning that you might get if you open a page or post for editing in Page Builder:

This post has a Theme Builder layout assigned to it. Using Page Builder here will override that layout. Do you want to continue?

In most cases, this warning arises for Singular-type Theme Builder layouts that apply to the page you're opening for editing in Page Builder. The Singular layout is the only theme layout that includes the content area of the page. The content area in the theme layout uses the Post Content module. When the theme is applied to a single page or post, the Post Content module takes the content from the native WordPress editor. This means that you cannot use Page Builder to lay out the content area on pages or posts to which you want the Singular theme layout to apply.

If you choose to open Page Builder to lay out the content area of a single page or post that has a Singular theme layout applied to it, the theme layout will be overridden, and your active theme will take control of all the areas of the page except the content area.