Hi Lucase,
By default, the Excel settings for groupings are set to "Summary Rows Below Detail" and "Summary Columns to Right of Detail". Here are the steps to change the vertical or horizontal direction of Excel's Outline Groups:
- Select the Data Tab
- Within the Outline group, click the dialog launcher button
- The two checkboxes within the Direction section of the Settings Dialog box will allow you to control which direction your outline groups expand/collapse
- Click the OK button

If you happen to need to modify these outline group settings with VBA code, the following snippets show how on the currently viewed spreadsheet.
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'Collapse Detail is Located Above the Total Row (Summary Row Below)
Sub CollapseRowsBelow()
ActiveSheet.Outline.SummaryRow = xlBelow
End Sub
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'Collapse Detail is Located Below the Total Row (Summary Row Above)
Sub CollapseRowsAbove()
ActiveSheet.Outline.SummaryRow = xlAbove
End Sub
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Best Regards,
Snow Lu