I will admit finding the visibility toggle setting took to me ten minutes or probably more, as it is hidden among many other settings, but at the end I managed locating it:
Go in the 'Bones' tab and thick the 'Show' checkbox, right click on the bone that you want to do invisible and select 'Edit' in the following tree view expand the 'ExtendedData' group, scroll down towards the end of the list, look for another group called 'MaxProperties and expand it. The property that you want to edit is the first one: 'Hide'; 0 = false (bone and relative mesh are visible), 1 = true (the bone and the mesh bound to it are invisible).
That's it
