"can I merge all the daily account summary amounts into an .iff transaction block? i.e. as if the day is a single transaction."
You can make One Transaction or as many as you need. Any Transaction can have a bunch of different Split lines, and you can even end a Sales Receipt at 0, since everything else was controlled. I don't know what "merge" and "block" mean to you.
Yes, a method is called "Daily Sales Summary" = One Transaction. Example: A POS system has a Z-out tape and we want to turn that into a Single QB import. It is done as a "CASH SALE" = Sales Receipt, for Import.
Let me help:
Stop using Journal Entry like this. JE first line is called Source; split lines are Targets. Stop using AR; I already explained that Problem. You also cannot use AP like that, for the same reason that Names are required.
AR = someone owes you. Someone Specific. AP = you owe someone; that Specific Someone. AP and AR rely on the Realtional Database to include Names. You cannot use AP and AR Generically. If you want Generic like that, this is Other Current Asset and Other Liability. Not AR and AP. And even if you tried this with names, you cannot put Both in one transaction. Think of AR and AP as "reserved functions for those people using the program's Intereface" which you are Not Doing.
Using AP and AR means you would still need to have the Linked Transactions; you cannot have Linked transactions from the .iif process. Even if you list AR and "debit and credit" with the same one name, those are not Linked. Even if you use Bill and Bill Payment for AP, using JE or even the real transactions, they are not Linked from the .iif process. You are mixing your processes.
You have Checking as Negative, but Cash as Positive?
Let's start over: what are you trying to show? Type out the Function here, such as:
I sold $x, I paid for $y, I got paid $a, I transferred $c from checking to savings, etc.
Give us Words, please. We cannot tell you if the coding is what you want, when we don't know the End Goal.