I'm really excited and happy that we can now create webhooks in workflows. But...
There is currently NO way to use these fields in custom code. They appear there, but they are greyed out. Why this is a big issue, is that I have to use "Format Data" actions to store the data from the webhook, and then I can use the output from these Format Data actions in the custom code action. This is a laborious and inefficient way to use the get the data.
So, the webhook functionality is a great addition, but it is severely hamstrung by not having the fields available in the Custom Code actions.