You can use the following macro expressions to get step data within the context of the document wizard:

FirstStep

 {% DocumentWizard.FirstStep.StepIndex %} :  0
 {% DocumentWizard.FirstStep.StepUrl %} :  /Examples/Web-parts/Document-wizard/Introduction.aspx
 {% DocumentWizard.FirstStep.StepData["NodeName"] %} :  Introduction

PreviousStep

{% DocumentWizard.PreviousStep.StepIndex %} :  1
{% DocumentWizard.PreviousStep.StepUrl %} :  /Examples/Web-parts/Document-wizard/web-parts.aspx
{% DocumentWizard.PreviousStep.StepData["NodeName"] %} :  Web parts

CurrentStep

{% DocumentWizard.CurrentStep.StepIndex %} :  2
{% DocumentWizard.CurrentStep.StepUrl %} :  /Examples/Web-parts/Document-wizard/macros.aspx
{% DocumentWizard.CurrentStep.StepData["NodeName"] %} :  Macros

NextStep

{% DocumentWizard.NextStep.StepIndex %} :  0
{% DocumentWizard.NextStep.StepUrl %} :  
{% DocumentWizard.NextStep.StepData["NodeName"] %} :  

LastStep

{% DocumentWizard.LastStep.StepIndex %} :  2
{% DocumentWizard.LastStep.StepUrl %} :  /Examples/Web-parts/Document-wizard/macros.aspx
{% DocumentWizard.LastStep.StepData["NodeName"] %} :  Macros

Step collection

{% DocumentWizard.Steps.Count %} : 3
{% DocumentWizard.Steps[0].StepIndex %} :  0
{% DocumentWizard.Steps[0].StepUrl %} :  /Examples/Web-parts/Document-wizard/Introduction.aspx
{% DocumentWizard.Steps[0].StepData["NodeName"] %} :  Introduction