DITA topicref attribute @search (with value yes or no) allows you to specify whether the referenced topic is to be included in full-text search. DITA2Go excludes from OmniHelp full-text search topics that are referenced with @search="no".
If your DITA maps do not include values for the topicref @search attribute, you can achieve the same effect with PI markers inserted in the topicrefs, and a ditaval file. For example:
In this example, the effect on DITA2Go output is the same as if you had included @search="no" in the topicref for each such topic. You can get the same effect by placing the PI marker inside the <title> element of the topic.
You can achieve paragraph-level search granularity with PI markers placed within a topic; the last Search value in a paragraph applies to the entire paragraph.