Use the "Delete" button on the Responses tab to delete responses and associated Nodes. To delete a response:
Click on the Response to delete in the table on the bottom half of the form.
Click the Delete button.
If the Node associated with the response just deleted is not used anywhere else in the Call Tree, that Node and all Nodes beneath it that become unused will be deleted from the tree. The Node will not be deleted as long as it is still used somewhere else in the Call Tree.