Not sure if I'm missing something here, but when I run an Itemized Tags report from Spending, the report is correctly grouped by Tag, and defaults to sorting by Account / Date. In the Sort by drop down, there is an option to sort by Category, which you can select, however I don't see the Category shown anywhere in the report. Note that the Tag is shown twice, once as the group header, and again in the body of the report. But nowhere do I see the Category even though it is a Sort By selection.