Hello Cha,
At the moment, it is not possible to change the key bindings in Fusion. However, there are other ways to perform view orbit/rotation. See the attached picture - there are two ways to invoke orbit as a standalone command (not required to hold down a key). You may also click and drag the left mouse button anywhere on the "view cube" in the upper right hand corner. As you drag, the view will rotate.
Regards,
Jeff Strater (Fusion development)
Jeff Strater
Engineering Director