Notenik endeavors to be both powerful and flexible. So the Seq field can be used to put notes into sequence using any sort of arbitrary value but, by definition, it is not necessarily unique. Nor need it be, in cases where notes are identified based on Title alone, or in combination with a Seq field. So Notenik tries to be helpful, but also tries to avoid presuming too much about what you are trying to do.
However in a case like yours, where you are using a Seq field as the only note identifier, I’ve modified Notenik to keep track of the highest seq value yet used, and then to increment that value when preparing a new note to be filled out.
So try out the latest beta and let me know how this works for you.