Firefox 87: hitting enter at "Enter search terms" doesn't go straight to search engine homepage

Question

In Firefox 87, keyword searching with an empty keyword doesn't go straight to the search engine's homepage when I press enter; it forces me to enter a search term when it says:

Is there a way to restore the old behavior, so hitting enter goes straight to the search engine's homepage?

_{cf. r/firefox "Why is custom search broken now?"; allegedly, this is part of the so-called "Design Update 2".}

Answer 1

Add a bookmark and set its keyword to the key sequence you want.

"Use a single keyword to open bookmarks directly from the address bar".

For example, you could set "so" to go to StackOverflow, even if "so" is already bound to the StackOverflow search engine.