Thanks, good suggestion. I do have this field displayed, and I recommend this to anyone else whose search gets them to this post. (I also strongly recommend monthly account reconciliation so you can discover and true-up any issues within the scope of just one month.)
To give additional context around my initial post, in case it helps: I'm going into reconciled credit card transactions to retroactively itemize within them, to use Quicken reporting to get a better understanding of our monthly spend over the past year. Through this process I managed to change the dollar amount of a top-level transaction, which I could tell because my current balance was now off from my bank by $32.25. I tracked it down by walking backward through monthly reconciled amounts until I found the month where the change occurred. I then walked through the likely transactions in that month until I found the one with a newly itemized entry that matched the dollar amount of the account's balance change. Fortunately it was only one transaction! A warning, though, at the point where my work changed the previously-reconciled transaction's amount in the first place would have helped me avoid that work.
Thanks, again, for your reply. I already have a positive impression of Quicken, and it makes me feel even better about Quicken knowing that these posts are monitored and that helpful tips are forthcoming. This has been a very positive interaction.