Group Detail Rows with Expandable Outlines in Gnumeric

An outline lets a reader collapse detail while keeping a summary visible. It does not aggregate records automatically, filter by a condition, delete hidden cells or protect their contents. Build the summary formulas first, then group only the detail rows.

Scope: free Gnumeric desktop on Linux, English controls from official 1.12.62 source and the 1.12 manual, reviewed 21 October 2026. Native grouping, screenshots and save/reopen checks were unavailable. Expected totals were independently calculated; visible control behavior remains to be checked in your installed build.

Build two sections with separate totals

On a new sheet named Plan, enter this layout. Leave rows 6 and 11 empty.

Row	A: Item	B: Amount or formula
1	Item	Amount
2	Desk supplies	100
3	Packing materials	60
4	Labels	40
5	Materials subtotal	=SUM(B2:B4)
7	Local delivery	30
8	Collection	50
9	Handling	20
10	Service subtotal	=SUM(B7:B9)
12	Grand total	=B5+B10

Expected B5 is 200, B10 is 100 and B12 is 300. Save a checkpoint before changing the display.

Do not use =SUM(B2:B10) as the grand total: it includes the detail and both subtotals, producing 600. Hiding the detail does not fix that double counting. The correct formula deliberately adds only the two subtotal cells.

Group only the first section’s detail rows

1. Select the entire row headers 2 through 4, not just the visible text cells. Leave subtotal row 5 out of the selection.
2. Choose Data → Group and Outline → Group. If your selection leads to a Rows/Columns question, choose Rows.
3. Inspect the left edge of the grid for an outline control associated with those rows.
4. Select the same detail rows and use Data → Group and Outline → Hide Detail, or use their outline collapse control.
5. Confirm rows 2:4 are hidden while row 5, row 10 and row 12 remain visible. Their values must still be 200, 100, 300.

The Gnumeric menu manual describes the outline feature. Exact Group, Ungroup, Hide Detail and Show Detail commands and row-selection behavior were checked in official 1.12.62 source, src/GNOME_Gnumeric-gtk.xml and src/wbc-gtk-actions.c. The manual’s separate grouping subsection is unfinished, so it is not treated as evidence for undocumented dialog details.

Add the second section and expand safely

Select entire rows 7 through 9. Apply Group, then Hide Detail. With both groups collapsed, the two subtotal rows and grand total remain visible. A report showing 200, 100 and 300 is the intended summary, but inspect row numbers to verify the correct detail ranges were hidden.

Use the first group’s expand control to show rows 2:4 again. Alternatively, enter A2:B4 in the name box and choose Data → Group and Outline → Show Detail, selecting Rows if asked. Expand the second group similarly with A7:B9. These ranges deliberately exclude the summary rows.

Display controls may appear above or below an outline depending on worksheet settings. In the reviewed source, Data → Group and Outline → Display Outlines toggles their visibility. Showing the controls is not the same action as ungrouping the rows. If you cannot identify a group reliably, use the explicit range and Show Detail command rather than deleting rows.

Change a detail value and recheck the summary

With all detail visible, change B3 from 60 to 75. B5 should become 215, B10 remain 100, and B12 become 315. Collapse the first group again: the same three results must remain visible.

The independent calculation is 100 + 75 + 40 = 215, then 215 + 100 = 315. This confirms that the summary is connected to the source cells rather than being a manually typed total. Re-expand, restore B3 to 60, and confirm 200 and 300 again.

This model uses SUM and explicit subtotal references. It does not claim that every function treats hidden or filtered rows identically, and it does not use visibility-aware subtotals.

Remove an outline without removing the data

Expand the first group fully. Select entire rows 2:4 and choose Data → Group and Outline → Ungroup. Confirm its grouping control is removed while the three inputs, subtotal formula and grand total remain. Repeat for rows 7:9 if you want to return to an ungrouped worksheet.

Expanding before ungrouping makes the reset explicit. Do not use Delete Rows: that is a data-editing operation, not outline removal. Keep a backup if you are removing unfamiliar or nested groups from an existing workbook.

Troubleshooting and final checks

• Subtotal vanished with detail: the group includes its summary row. Expand, ungroup the mistaken range and group only 2:4 or 7:9.
• Outline brackets are missing: inspect Display Outlines before assuming the grouping was lost.
• Grand total is 600: inspect the formula, not the display. It is probably adding both detail and subtotal rows.
• Hide/Show Detail reports no existing group: check the selected rows and whether Group was applied. Ordinary hidden rows are not necessarily an outline group.
• Need categories selected by value: use sort and filter instead. Outline boundaries follow selected row positions.

Save as .gnumeric, reopen, verify both totals and inspect whether the intended groups and expanded/collapsed states persisted. This final native check is still pending for the example. Grouping is a presentation aid, not a confidentiality boundary: hidden detail remains part of the workbook.