@leocg is it not possible? because the tab with the functions are available, it is the exact same as that of Google chrome.
Link Opera: opera://settings/searchEngines
Link Google: chrome://settings/searchEngines?search=sear

even setting up the custom search engine is exactly the same.

I wish to use the site search function from Opera for youtube. The problem is that I can't get it to work.

To search you would need to fill out three things: 1. The name or title of the search engine (Youtube), 2. The Shortcut (Https://youtube.com) or (youtube.com), 3, URL with %s in place of query (https://www.Youtube.com/results?search_query=%S&page={startPage?}&utm_source=opensearch)

The idea is that you type in your searchbar youtube and press space or tab to specify what you want to search

I know it possible in Google chrome and I wish to also use this in Opera. Could some please tell what I'm doing wrong.