I am not sure what that 'hidden requirement' might be, but technically there is nothing else besides posting completed items in this forum. If you choose to go for the November Merit Badge, it is good to have an account at NaNoWriMo,org, but for the October Prep Merit Badge, I don't think that is a requirement. Everything else would be optional.

Brandiwyn🎶 may be able to clarify what the 'hidden requirement' might have been, but I am drawing a blank.