Help center only searches the currently visible page. The search should be able to find topics and other words via searching the entire handbook  (stay withi9n the application handbook).
For example, if I bring up the Kate Handbook I should be able to find any page in the handbook that contains the word (or partial word) 'diff' in it so i can find out about Kates diff view but it should not bring up other applications info. I dont want info on the command line app diff for example only as it relates to Kate (in my example) although this could be some kind of checkbox option much like 'man -K'