itemsInColumn property ignored in GroupItemDef

[arnoldas-v]

Describe the bug

GroupItemDef does not respect itemsInColumn property

To Reproduce

Create a GroupItemDef with multiple items and define itemsInColumn property to 1

    items: [
      new ToolItemDef({ toolId: "0", label: "0" }),
      new ToolItemDef({ toolId: "1", label: "1" }),
      new ToolItemDef({ toolId: "2", label: "2" }),
      new ToolItemDef({ toolId: "3", label: "3" }),
      new ToolItemDef({ toolId: "4", label: "4" }),
      new ToolItemDef({ toolId: "5", label: "5" }),
      new ToolItemDef({ toolId: "6", label: "5" }),
      new ToolItemDef({ toolId: "7", label: "5" }),
    ],
    itemsInColumn: 1,
  })

Result: grouped by two columns (see screenshot)

Expected Behavior

List displayed in specified number of columns (1)

Screenshots

Desktop (please complete the applicable information)

Windows 11
electron 25.8.1
iTwinJs 4.4.3
appui-react: 4.10.0

Additional context

No response

[GerardasB]

GroupItemDef is a legacy way of providing toolbar items and should be deprecated.
Instead please use https://www.itwinjs.org/reference/appui-react/toolbar/toolbaritemutilities/ to create the toolbar items.
https://www.itwinjs.org/reference/appui-react/toolbar/toolbargroupitem/ currently doesn't have the itemsInColumn property and there are no plans to support that behavior.
However, we are working on a toolbar replacement #602 that is planned to have a single column group.