"Is there another way to enter the total RMD due for all accounts?"
You don't enter the total RMD on your tax return.
"But my concern was how does the IRS know that the total distribution was sufficient for the sum of all account RMDs if it doesn't know the RMD for the accounts that did not have a 1099-R?"
As Mike9241 explained, the IRS knows the RMD for all the accounts because they get a copy of the Form 5498 for each account from the custodian. The 5498 shows the RMD for every account, whether or not you took a distribution from the account.
