A Couple of Years ago, Google introduced the Sitelinks Searchbox. When Activated, this Search Box appears under the main URL for a Given Brand in the Search Result, above its sitelinks, hence the name. When you search for that Brand in Google, you can directly use the site’s Search Engine.
The Result will be Presented on the search Result page of the relevant Site.
How to add a Sitelinks Search box to your Site.
Adding the markup is simple if you’re on WordPress and use Yoast SEO. in that case, all the necessary code will be added automatically. There are exceptions of course: It could be that you don’t use the default search engine, in that case, you need to change the URL using the Built in Filter.
If you don’t use Yoast SEO, you can add the necessary code by hand via a Piece of Schema.org Structured data. The Screenshot below shows a Piece of Example code from Google’s documentation in the Same document you also find the requirements for a valid technical implementation. This uses JSON-LD to mark up the code in an efficient and Readable way.
Set ups a Preferred canonical URL for your Homepage (Yoast SEO does this automatically)
Chek the Sitelinks Search box Result in Google Search Console
A few days after enabling this you should have a Sitelinks Search box report in Google Search console.