@paolone
On AmigaOS UI the most coherent place would be the left side because you already close other GUI elements (e.g. Windows) with a gadget on the left.
Putting close gadgets at the right of the tabs will confuse amigans since amigans have close gadgets at left. Putting the close gadget at the right on MS Windows is the best place since the user closes the windows with a gadget located at the right.
Anyway if the close gadget of the tabs was configurable problem solved for those people who is used to alien OSes with close gadgets on the right.
PS: Stanislaw has done a great work :-)
PS2: But I hope he makes the position of the tabs close gadget configurable and that he locates it at the left so it follows AmigaOS UI style.