URL bar shortcuts for websites and search engines
This is functionality that I haven't quite seen yet in a mobile browser, but it does exist in desktop browsers (such as Vivaldi). Allow the user to define multiple custom search engines, and provide each with a shortcut so when you search for something, you can type the shortcut followed by the search criteria.
For example, define search engines (or actual search URLs, however necessary) as so:
Then type search criteria such as:
"g Portland, Oregon" - searches for "Portland, Oregon" using Google
"ddg search engines" - searches for "search engines" using Duckduckgo
I don't know how easy this would be to implement in a mobile browser, but in Vivaldi, you just give a friendly name, the URL, and a shortcut.