A design management role is going to be more about your achievements. What have you put out, what have you succeeded at. From a process perspective it is less about how hot your sketches are but to show how you are capable of leading a design organization.
The work you show should demonstrate:
-How have you created alignment and solved complex problems?
-How do you treat things like design vision, design language?
-How have you helped to shape the outcome of projects?
Including the work from your current Sr Designer role is fine if you think it shows valuable skills, but the big gap between a great senior designer and a great design director is your ability to craft a vision for the larger organization, and those skills are what you want to highlight.