//  You can use either the control's GroupSettings or the settings object
//  for a specific group.
//UltraExplorerBarGroupSettings groupSettings = this.ultraExplorerBar1.GroupSettings;
UltraExplorerBarGroup group = this.ultraExplorerBar1.Groups[0];
UltraExplorerBarGroupSettings groupSettings = group.Settings;

//  Set the Style property to 'ControlContainer', so that no items
//  appear, and a container control is displayed instead.
groupSettings.Style = GroupStyle.ControlContainer;

//  Set the 'ContainerHeight' property to change the height of the
//  group (applicable only when the group is expandable, as is the
//  case when the control's Style property is set to 'ExplorerBar'
//  or 'VisualStudio2005Toolbox').
groupSettings.ContainerHeight = 300;

//  Create an UltraTree and add it to the group control container's
//  Controls collection.
UltraTree treeControl = new UltraTree();
treeControl.Nodes.Add( "One" );
treeControl.Nodes.Add( "Two" );
treeControl.Nodes.Add( "Three" );
treeControl.Dock = DockStyle.Fill;

group.Container.Controls.Add( treeControl );

How to do it from the code ?

 Thanks in advance,

 Thomas