Hi David,
You can use the following workaround: add the "RequestFilter.filterRequest" event handler with the groovy script which adds custom HTTP headers (Set-Cookie).
The groovy script can be like this:
def headers = request.requestHeaders
headers.put("Set-Cookie", "valueFromRawResponse1")
request.requestHeaders = headers
Note that the event handler can be targeted to only run for a specific test step or group of test steps.
Please refer to the following articles for details:
Events: http://readyapi.smartbear.com/readyapi/events/handlers
Adding custom HTTP headers: https://www.soapui.org/scripting-properties/tips-tricks.html#12-Add-custom-HTTP-header-to-requests