How do I examine the workflow task instance. I would like to see the all the top-level workflow variables

Pages based on GenericEditForm all ultimately do their thing in a *Viewer class in the session package.

Something that can come in handy trying to debug workflow problems like this is to dump the workflow task to a file. Insert an Action like this:

<Action>

  <expression>

    <invoke name='dumpFile'>

      <invoke name='getTask'>

        <ref>WF_CONTEXT</ref>

      </invoke>

      <s>c:/temp/workflow.xml</s>

    </invoke>

  </expression>

</Action>

What this does is generate a file containing the XML for the TaskInstance that holds the state of the workflow process. In here you can see all the top-level workflow variables near the top under a <Variables> element.