This shortcut demonstrates how to get a JSON variable instance using the HTTP API, convert it to a shortcut dictionary, then use the value from the dictionary to set the value of a different variable to the value of the first.
Download and unzip. Then, double-click on the shortcut and it'll import it into the Shortcuts app.
Once imported, you should edit the shortcut to see the comments, the items to configure, how it's all put together and to run it in your environment. It's a good example of both getting a variable from Indigo, getting parts of the reply, and setting the value of another variable.