https://www.techrepublic.com/article/add-gmail-search-engine-chrome/
…How to add Gmail as a search engine
Open your browser and then open the Settings window. From there, locate the Search Engine section and click Manage Search Engines And Site Searches
In the resulting window you’ll see all of the default Search Engines listed
Below that, you’ll see the Site Search section, which will list all of the custom search engines you’ve added. Click Add. In the next window here’s what you need to paste into the settings:Search Engine: Gmail
Keyword: gmail
URL: https://mail.google.com/mail/u/0/#search/%sAfter configuring the new Search Engine, click Save to dismiss the window. Your new Gmail Search Engine has been added.
Open a new tab and type “gmail” in the address bar followed by a space. Type the search query you want to run in Gmail and hit Enter on your keyboard. This will open the tab in Gmail with the results of your search.
One thing to know is that you don’t have to use the default Google search engine for this to work. I tested the feature with DuckDuckGo listed as my default search engine and all worked exactly as expected…
