d4pSidebarAnchor indicates where in the document a sidebar topic should appear. Sidebars are tricky to place in a hierarchical order, because they often contain content that can appear at one of many points in the document. Furthermore, because a sidebar is a topic type, sidebars must always go after a previous topic's body, which may be many paragraphs from the author's intended location for the sidebar.
d4pSidebarAnchor is specialized from xref. A processor should replace this element with the actual sidebar content and ensure the sidebar content does not appear twice.
+ topic/xref d4p-formatting-d/d4pSidebarAnchor