Why the switches for climb and cruise ratings. What was being accomplished that modulation of the throttles couldn't
Basically because we operated the Concorde at full throttle all the time except for noise abatement until decel / descent. The schedules and ratings fine tuned the full throttle performance according to a tightly tuned regeme - and reheat was selectable on switches rather than throttle lever angle because we spent most airborne time supersonic at full (dry) power without reheat. At the time that was the unique achievement of Concorde: reheat was used for a tiny proportion of the flight and so was relegated to four little switches. It wasn't even used for a go-around. Even on three. But that's another story.