New report that will show online balance and ending balance or each account. Could show difference. To easily see if there are discrepancies without having to open each register.
One problem with implementing this is that "Linked Checking Accounts" (i.e., the pseudo-checking account created by the "Show Cash in a checking account" option) don't have an "Online Balance".
And, at least for my wife and I, our respective LCAs are our primary checking accounts.
Also, this would presumably only apply to accounts enabled for download and only for Banking type accounts. Since I only have 8 accounts that satisfy this criteria, it's easy enough to just look at the account register … so I don't see that a report is worth the effort it would take Q to create.