The IAS hold in the pitch mode as used every flight as it was SOP for a decent.
Alt Hold engaged
Throttle back the engines to an intermediary point.
When speed came back to 350knts engage IAN hold to start the decent all the way at 350knts until a primed new altitude was reached, where the aircaft would level and the Autothrottles would come back into play
For sustained decent at M0.95, Mach hold would be used.