Not so easy to do in these days of RVSM and RNP. And hand flying in straight and level flight or even on an ILS with auto thrust and flight director engaged does little to enhance anyone’s manual flying skills.
DHC8 driver,
Maybe it will come as no surprise to you, but based on now 50+ years flying, and 35 years in airlines, with the usual Check and Training stints, and with little real change in the "technology" in the last 20, I totally disagree.
Indeed, hand flying straight and level can really sharpen up the scan.
It doesn't have to be a raw data hand flown ILS (or any other approach) to be of value in keeping up hand IF and visual flying skills.
Company/manufacturer "recommendations" to leave the auto-throttle engaged when hand flying are seriously misguided.
Tootle pip!!