When I teach RoboHelp, I tell my students and the three main areas users will rely on to get help in a help system are the table of contents (TOC), Index, and Search. Of the three, Search wins the award for being the most used feature.
One thing to avoid in a TOC is bloat--a TOC that has so much content that it's difficult, if not impossible, to find anything quickly. Because users will first rely on Search, keeping the content on the TOC streamlined is a great idea. However, if a topic is not on the TOC or referenced by a link or cross reference by something on the TOC, the topic won't be searchable. This presents a conundrum. If you want to keep your TOC streamlined, but the TOC is tied to Search, what's a RoboHelp developer to do?
The solution is to create an extra section on the TOC. Put anything you want to be searchable in that section. (You can add all of your topics if you'd like.)
On the Content Properties panel, select Hide in output.
Generate the output. The "hidden" TOC content will not appear on the TOC, but will be searchable.
Check out this video demonstration of the process.