There are two sets of budget reports in QuickBooks Online, namely, Budget vs. Actuals and Budget Overview. This is the reason why we're currently unable to merge elements on both reports.
If you want the Budget vs. Actuals to have a column for the total annual budget, you will need to pull up those 2 reports and customize them in Excel. To do the export process, use the Export icon so you can start modifying them on the worksheet.
I'll be adding some related links to help you get your way around the Reports feature in QBO:
I know I can do it myself. I was hoping there was a way to do it in QBO since I already have to pull 2 reports for Budget vs Actual, one for the month and one for the YTD, which also can't be done on one report. So, now I have to pull 3 reports and combine them in excel just to get what's needed, for each and every class and for the overall. That's a lot of manual steps for an accounting system that should be able to do it for me.