Check out Reuse with the Learning and Training specialization by Kaitlyn Heath. Here is an excerpt:
You have your technical content in DITA, and you are reaping the benefits of reuse. Now it’s time to move your training content over, but it’s a little confusing to figure out how to structure your content with DITA Learning and Training elements. How can you best set it up to facilitate reuse…
The full article is available here.