Справка LibreOffice 24.8
Defines the selected cell range as a group of rows or columns.
When you group a cell range, and outline icon appears in the margins next to the group. To hide or show the group, click the icon. To ungroup the selection, choose Data – Group and Outline - Ungroup.
Groups the selected rows.
Groups the selected columns.
Grouping and ungrouping is not tracked. Group is greyed out when track changes is on.