You aren't required to submit your assignments, except for the contest rounds (which is only required if you are competing in the weekly contests.)
Although I do post mine, I don't bother submitting the links (except, again, for the contest rounds.) However, I did submit some in past years. When the required and bonus rounds weren't separable (today's brainstorming would have been such a case) I just submitted the same item ID for both required and bonus assignments.
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Regards,
Eric Fretheim
Assistant Prep Leader, 2015 October NaNoWriMo Prep Challenge

"It is perfectly okay to write garbage-- as long as you edit brilliantly." ~C.J. Cherryh

“No, writing 50,000 words in a month is normal. You are not crazy. This is not insane.” ~Teri Brown