So what are we aiming for?
(a) Minimum/flattest descent angle/best glide range? Sounds like an AoA or IAS at given weight for best Lift/Drag ratio.
Or
(b) Minimum descent RATE? at a slower IAS and higher AoA giving a steeper descent angle and reduced glide range, but perhaps more time at a higher altitude that may give higher TAS and lower specific fuel consumption.
????