This finally allowed me to get QBO to actually compute ST.  Thank you!

I am wondering why QBO is unable to do this automatically without clicking the "Tax" box on each line item for an invoice?  Product and customer are both marked as taxable in advance of invoice creation.  

QBO's attempts to automatically calculate based on location are simply wrong.  The automation basically just interferes with me applying the correct rate to my customers.  No one asked for this program to make wrong guesses about Sales Tax and them try to prevent correcting its wrong guesses.

Further tip to everyone:  Sign up for an accountant account then make yourself the accountant of your company.  Your real accountant can still be associated because 2 accountant accounts are allowed.  This will allow you to delete QBO's automated, error ridden sales tax guesses and replace it with a correct (manually created) return.

The accountant features also allow you to perform basic tasks which Intuit seems to think should off limits to regular business people, such as easily viewing account bank balances in one screen.  Or fixing a ST return.  Or reclassifying several transactions at once. It's a breath of fresh air compared to the normal, dumbed down user interface.

The accountant features go a long ways towards making QBO usable to people who do understand their books.  It's your "get out of kindergarten free" card. 

Still looking for why QBO cannot assume line items are taxable.  None of the instructions here got me that far.  Fortunately I mainly use Harvest for invoices and it does calculate ST correctly and easily...you know, in the manner every accounting program ever, other than QBO.