Sort by Subtotal
If you try to sort an Excel spreadsheet that has subtotals, Excel gives you a "This removes the subtotals and sorts again..." message. This is fine if you want to sort the underlying rows differently, but what if you want to sort by the subtotals themselves?
To do that, you need to collapse the display so only the subtotals are showing and then do a sort. This will sort by the subtotal, but not the underlying rows. To collapse the spreadsheet so only the subtotals show, go to the subtotal levels that display on the left hand side of the spreadsheet and click the number at the top that corresponds to the subtotal level that you want to use to sort. The number may change depending on how complex your spreadsheet is, but in general level 1 shows only the grand total and the last level on the right shows all details. You may need to experiment to figure out which level is the one you need to use. In this case, it's a simple subtotal so the level is 2.
This collapses the spreadsheet so only the subtotals are showing. When the subtotals are collapsed, you'll see a + sign in the box to the left of the subtotal instead of the - sign.
Once everything is sorted by the subtotal, you can sort as normal. If you want to see the details for all of the subtotals again, click on the level button on the right hand side. In this case, it would be level 3.