GroupDisplayMode

Specifies the visualization mode for grouped data in the Grid.

• 'default' — An empty indent cell is inserted per group level before each row, visually reflecting nesting depth via horizontal offset.
• 'compact' — Removes the empty indent cells. Group header rows span the full column width, improving data density in grids with many group levels.
• 'singleColumn' — Consolidates all group levels into one dedicated left-positioned group column. Nesting depth is conveyed through increasing left padding inside that column. Long group titles truncate with an ellipsis.
• 'multipleColumns' — Renders one dedicated group column per active group level. Each column displays the value for its corresponding hierarchy level. Long group titles truncate with an ellipsis.