Is there an alternative way to add links on 'One-Click Search Engines'?

I want w3schools website on 'One-click search engine' to search within address bar by using keywords. Unfortunately, add option doesn't appear on search bar. I don't know if it's a bug or not. If not, then sure it has another way to put it in search suggestions.

Now I'm very use to 'One-click search engine' feature that lets user to search directly to that webpages by using keywords. So if there's any alternative way to add websites into search lists, just let me know. :)