Search in option should show same popup as quicksearch, but only with options keywords.
The global quick-search is used to search for pretty much everything so it is good that you can specify the scope of the search plus you get some suggestions based on what you already have typed.
On the other hand, in the options window case the user knows the scope and what to search for.
It sounds like a nice addition but I believe that it would create too much clutter in the options window.
Look on intelj idea how search in options work. You press one key and it already shows you only options that starts with this key. User sees immediately that search is working. This is a core functionality in all option search.
Same functionality as quicksearch was one idea. Searchbar is also searching immediately.