Is there a way to assign shift key to a mouse button? I have a Spacemouse and in Blender for Mac, the Spacemouse settings do not work, so if I need to assign specific buttons, I need to do it via Blender. I would like to use one of the keys as a shift key.
I think blender maps operators to keys and not keys to operators, so you probably have to remap every operator that uses the Shift key.  

In user preferences->input ,  you can set the input event to a NDOF device.