You now have the ability to fully edit assignments after creation! You can edit the name, description, and due date! It isn't currently possible to change the assigned class in the app, but if this is something of interest, reach out to the Support Team directly in the app!
To edit an assignment on iOS:
Head over to the Assignments tab in the app
Tap the assignment in which you wish to edit
Choose the Edit Assignment option
Make your changes and save!