MY_GPIO.borrow(cs).borrow().as_ref().unwrap().odr.modify(|_, w| w.odr1().set_bit());

or

  let mutex = MY_GPIO.borrow(cs).borrow().as_ref().unwrap(); mutex.odr.modify(|_, w| w.odr1().set_bit()); 

Both of those ways are really horrible, and differ almost nothing. I understand and know why it looks like it does, but having to jump through all that mental gymnastics just to understand/write one line is why Rust is just overly verbose for a lot of things.