Notice: This will not work until DCR Portal 6.9 is released in August 2023.
The logic works as follows.
First, the user enters the name of the city.
Doing this makes the "lookup" activity pending (the blue response arrow), so the robot executed the lookup activity which invokes a HTTP GET as a side effect. The data returned is a json structure.
Once executed the form is included and values are copied over from the json structure using DCRJsonLookup(WeatherService,'cityname')