This is a bit of a tangent, but note that you don't have to
create separate topics with duplicate information. For example,
let's assume that your Help system contains two books based on the
two modules available in your software: Module A and Module B. Your
books might be set up like this:
BOOK A:
* About Module A
* Feature A-1
* Feature A-2
BOOK B:
* About Module B
* Feature B-1
* Feature B-2
If you want to add the "About Module A" topic to Book B,
simply open the TOC tab, click Book B, click the new page icon,
enter a TOC title for the new page, and select the "About Module A"
topic from your topic list. So you could end up with this layout
for Book B:
* About Module B
* Feature B-1
* Feature B-2
* About Module A
Or you could end up with this:
* About Module B
* Feature B-1
* Feature B-2
* Additional Information (which has a different TOC title but
still loads the "About Module A" topic)