The present invention enables a system to efficiently maintain an ancillary pane containing a projection of document content, and content derived therefrom, while the underlying document is being edited. In one embodiment, an acronym pane displays a list of acronyms used in a document and one or more expansions of those acronyms. A data store containing maps is used to index which paragraphs contain which acronyms, and which acronyms are associated with which expansions. As sections of content are added, modified, or deleted, acronyms and expansions are added to and/or removed from the data store, causing the acronym pane to be updated.