@UnimpressedwithIntu1t  

"So historically when entering these bills, I enter the one with the most line items LAST. This is because I won't have to total up 30 or 40 line items at the end of my invoice to get a total for that last account.

Yes- you can put a formula into that box subtracting the QB tally and your invoice total. But it is still an extra step. All of QBO for me from desktop is a series of EXTRA STEPS that when all added up are taking time out of my day instead of saving me time."

You're not saying the same thing as the OP.  I get it what you're saying but that is not how the OP stated it.  Here is what the OP stated:

"Desktop would allow me to enter items and then it would calculate the total. Why not in QB Online?  This feature is particularly helpful if a vendor has multiple costs, items, etc on one bill and does not provide a total. Since switching from Desktop I cannot figure out how to do this without manually calculating each line item cost and total using a calculator."

"I know how to enter the total bill, just don't understand why I must calculate the total manually then enter the total. QB Online should have the capability to enter items on a bill then total that bill for you."

"When entering bills in QB Online the only option it to enter total. Desktop would allow me to enter items and then it would calculate the total."

There is no reason to need a calculator using QBO.  The OP said that "QB Online should have the capability to enter items on a bill then total that bill for you."  It does.  If your point is that you could enter a total in the AMOUNT DUE box on a bill in Desktop and then it would auto-fill the remaining amount due on the next line item, then that's true but not what this thread is about, or at least not how the OP stated it in any way.  I get it, your vendor bill has 100 line items, you enter the category comprised of the fewest items first, say 3 of the 100 items as the first line item.  Then, the next line item may be comprised of 10 of the 100 items.  Finally, the remaining 87 items fall into the last line item.  In Desktop the remaining balance would auto-fill - agreed that it was a nice feature.  In QBO, you just need to enter a quick formula on the the last line item.  It appears you have an axe to grind with Intuit.  You won't get any argument from me that Desktop is a superior product to Online - it is.  But, taking shots at people like me that are just trying to help other us is unnecessary.  QB Online is what it is.  Accept it and move on or find an alternative - you have options.