Hello @Sairam thank you for you idea. Currently we have the following behavior in place. When searching on the search bar of a parent or child category page, the results shown in the dropdown are coming from that parent on child category.  As such: 

Is this the behavior you were trying to describe?

@Marion Frecaut I am talking about automatically restricting the search per category, this is not doable at this point. 

@Marion Frecaut and also talking about search by username. It is request by our customers too.