How to transfer TestCase properties value in Authentication(Oauth2.0) Access Token field ?

I'm taking your code as a start,

def responseHeader=teststep.testRequest.response.contentAsString
def slurper = new JsonSlurper()
def json = slurper.parseText responseHeader
def token=json.access_token
testRunner.testCase.testSuite.testCases["login and update"].setPropertyValue("access_token",token)

 You are setting the test case level property here called "access_token". You can use the property expansion as ${#TestCase#access_token}. This will work only within the test case. The property expansion has to be modified if you need to access from a different test cases.

I would recommend to set it as a project level property, the scope is large. Here is the reference - https://www.soapui.org/scripting---properties/property-expansion.html

Thanks,

Kondasamy