Thanks HoneyLynn_G! I took a look at my tsheets settings, and the PTO codes are already correctly set up. Also, the QuickBooks Online Integration Preferences there already has every single checkbox enabled and checked. I even looked at the Payroll Item Mapping Tool, and it simply shows "Holiday" on tsheets mapping to "Holiday Pay" on Quickbooks and so forth for the other PTO codes that we have created.
However, the customize within "Time Activities by Employee Detail Report" still shows no way to distinguish a holiday pay item from a vacation pay item. In other words, there is no way for that report to print "Regular Pay" vs "Holiday Pay" vs "Vaction Pay", etc. So maybe as a previous reply mentioned there is some hack where a customer is created to represent each PTO category, but I am loathe to attempt that without having seen a working example first.
Also, thanks for the 3 links, however none of them mention this PTO code integration issue.