I selected use find dialg settings because it is faster change settings when you go from a type of documents to another going to the search windows (Ctrl + F) instead going into Configuration -> Preferences -> Highlighting.
But the fact is there is an option (Use Find dialog settings) that permits some operations that are disabled when another check is enabled. N++ has to remove that option (and not to sudgest to not use this because it doesn’t semm really useful) or has to set this option usefull.