Set shortcut to use 3DConnexion SpaceMouse button? How can I setup the right (or left) button on the 3DConnexion's SpaceMouse Wireless to act as &#9096; CtrlZ keystroke in Blender 2.7x for Mac? 

3DConnexion's own SpaceMouse settings don't work.
Try editing the keymap in &#9096; Ctrl&#9095; AltU> User preferences > Input.

To change a shortcut, click the button with the current shortcut and press the new shortcut. Pressing a mouse button works for me: