If e file was rejected and I have new forms to submit. How do I cancel return and start over?

Once the tax return has been filed you cannot clear the return and start over.

You only need to go to the sections where the forms can be entered and make your changes.  Once the changes have been completed you can e-file the tax return again.

You cannot clear and start over since you already passed the point of trying to e-file.  But if the return was rejected, you can make necessary changes or add information before you try to re-file.  You might need to click on Add a State to get back in to the return.  You do not really have to add a state; that "trick" will just let you back in so that you can enter more information or make corrections.  When you are done with all of that, you can re-file the return.