Thank you so much for this detail!

I must admit, I watched the video probably 4 times and reread your post at least a dozen times, to make sure I'm following what you are saying.

I did set up all the accounts you suggested, set up 2 vendor files for each - one taxable, one non-taxable. I created a sample one-day Sale Receipt to try out this process, but I must use the detailed line-by-line Sales Receipt. Since those lines were set up in Square as ITEMS, I needed to also set those up in Revenue. I created Farmers Market Sales Taxable and Farmers Market Sales Non-Taxable revenue accounts and coded those items as SERVICE to these revenue accounts. When I tried to set them up it would only let me put in a revenue account, not a Sales Liability account. 

Should I have set the vendors up as Non-Inventory instead of Service? I think I still would have to code them to only a revenue account in QBO.

At this point, would I then export the 2 Revenue account report to an Excel file, and upload to the appropriate Vendor files as BILLS with negative amounts? Or create a JE? I'm still perplexed as to how I will get the individual sales to each vendor.... 

Thank you for your kindness,,,,