The option to redetermine data structure is only available with the “custom webhook” module.
Also, I see that this app is using a shared webhook, therefore you will not see the webhook URL as well.
In general, if you want to predetermine the data structure for third party app (webhook-based), you just trigger the module, unlink all other modules from it, and then attach the rest of the modules (once data arrives) to view the modified mapping.