Use the workflow object. I know it's misleading because the object name is "workflow" not "workflowToken" but I tested it. For example, if you want to log the ID and start date of the current running workflow, put the following code in a scriptable task inside the main workflow:

System.log("Token ID: " + workflow.id);

System.log("Token Start Date: " + workflow.startDate);

System.log("Parent workflow name: " + workflow.currentWorkflow.name);

Hope this helps

Ali