This example demonstrates how to handle the PopupMenuShowing event to add new commands to the node menu:
private void treeList1_PopupMenuShowing(object sender, PopupMenuShowingEventArgs e) {
if(e.Menu is TreeListNodeMenu) {
treeList1.FocusedNode = ((TreeListNodeMenu)e.Menu).Node;
e.Menu.Items.Add(new DevExpress.Utils.Menu.DXMenuItem("Edit", bbEdit_ItemClick));
e.Menu.Items.Add(new DevExpress.Utils.Menu.DXMenuItem("Add child", bbAddChild_ItemClick));
e.Menu.Items.Add(new DevExpress.Utils.Menu.DXMenuItem("Delete", bbDelete_ItemClick));
}
}