I have solved the problem : there is an option for 2 buttons mouse in their tools setup. Now I can easily pan (Alt+right mouse button, which is emulated by pressing up the balance button of my pen) or rotate (Alt+left mouse button, which is emulated by holding down the balance button of my pen) and for zooming I use my mouse and I press Alt + the two buttons (the left before the right).

Kindly,
ivan

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botarosa