Yes. In the workout editor, drag and drop the exercises you wish to put in the superset.
Select the first and write the repetitions and in the execution field put "Superset 1" and press "Save" in the second exercise, put the repetitions and in execution field select "Superset 2" and continue this pattern until you have completed your superset. Be sure to press the "Save" button.
Then press the "Save" button for the workout plan. Press "Preview" to see how it will show up for your member via email.