Reusing DITA Topics in Multiple Maps

You can reuse a DITA topic simply be including it in more than one map:

To create a new map, select File > New or click the New button on the toolbar, select Framework templates > DITA Map, and choose the appropriate type of map.
Add existing topics to the new map by dragging and dropping them from the Project view or the file system (or right-click the map icon, or on a topic already in the map, and select Append child or Insert After).
If your topics use key references, set up the appropriate key definitions in your new map. You can set the keys when you add the topics, or afterwards by right-clicking the topic in the DITA Maps Manager, selecting Edit Properties, and defining them in the Keys tab.
If you want to define relationships between topics, other than those defined in the topics themselves, add a relationship table to your map or to a separate map linked to your main map.
When you have finished adding topics, check that your map is complete and that all topic links and keys resolve correctly. To do this validation, click the Validate and Check for Completeness action on the toolbar in the DITA Maps Manager.