Whenever I notice I missed something right away, I'll just go copy my original notes and resubmit. I used to withdraw, but resubmitting before approved/denined does that for you, it just leaves the old notes on the contribution notes page like antolod mentioned. Maybe I'll start doing the withdraw to keep the lists clearer, or maybe I'll ask what the preferred method is...

Do you want to see the old, nearly identical notes which will better show edits, process and such, or is it wasted space?

I'm good either way, just get everything right no matter how many small resubs end up being needed.