It’s also outdated in that Chrome no longer labels one of the items “keyword.” The keyword is the middle column, which defaults to the domain of the search engine. At the bottom of the list, where you can add new searches, the items are labeled, but it listed every search form on every page I’d ever visited, so I didn’t need to add them myself.
That Chrome link looks outdated. Chrome explicitly supports this feature now: Settings → Search → Manage search engines.
I used to do this but stopped for some mysterious reason I no longer remember.
It’s also outdated in that Chrome no longer labels one of the items “keyword.” The keyword is the middle column, which defaults to the domain of the search engine. At the bottom of the list, where you can add new searches, the items are labeled, but it listed every search form on every page I’d ever visited, so I didn’t need to add them myself.