Hi Ivan,
There are two ways to add a new tab item to a panel:
1) Via the update method of the Smart.DockingLayout. You can read more about it here. You can also modify existing tab items via this method by passing it the index of the target item. For example, dockingLayout.update(dockingLayout.items[0], { items: [ { index: 1, label: 'New Tab item' }] });.
2)Via the insert method of the panel itself. You can get a list of all panels of the Smart.DockingLayut via the items getter and then call the insert method of the panel. For example, panel.insert(1, { label: 'New Tab item' });.
Best Regards,
Smart HTML Elements Team