Before Google Maps got its new "full screen" look, I could open a URL that looked something like this "http://maps.google.com/?q=%s" where %s was a string of the format "from: London to: Amsterdam".
Together with the bookmark keyword feature of Firefox, I found this very efficient as it didn't involve mouse interaction nor waiting for the page to load before being able to enter something.
This no longer works as Google now searches for a place called "from: London to: Amsterdam".
I tried to adapt the URL to https://www.google.com/maps/dir/%s/ and %s having the format "London / Amsterdam" but this gets expanded to https://www.google.com/maps/dir/London%2FAmsterdam, which makes Google search for the place "London/Amsterdam" instead of a route.
TL;DR
How can I achieve it so entering something like "map from London to Amsterdam" into Firefox's address bar and then hitting enter gives me a route from London to Amsterdam?
I'm not tied to Google, though. Alternatives like Bing would also work as long as the calculated routes are usable for traveling by car.