How can I make use of the 4 (!) pedals shown in the Pianoteq interface?

I'd at least like to add an una corda and a sost. pedal, but my MIDI controller (Impakt LX88+) only has one phono jack, being used for the sustain ped.

So if there are MIDI pedals capable of being recognized by Pianoteq, which do you recommend?

I also have a Yamaha S80 which has an available foot controller ped. 1/2 jack. Any recommendations there?

I recommend the  use a class compliant USB MIDI pedal interface . In particular , the Midi expression Quattro made by Audiofront. 

https://www.audiofront.net/MIDIExpression.php

It accepts 4 midi pedals with tradition jack as in input and output all the midi signals via one USB cable (USB-B > USB-A) . The device comes with a great software which allows you to configure each pedal, and create specific curves for each independent pedal . In particular , you must assign to each pedal a Midi change controller number that matches the number declared in Pianoteq settings, so each pedal corresponds to the particular pedal in Pianoteq you want to control.

It accepts the quasi majority of pedals in the market, including the Kawai pedals type F10-H which are equipped with digital sensors and require 3.3v power.  The later is my preferred pedal in the market in term of quality, sturdiness and fine control. Roland DP10 is also a good pedal , not as good as the Kawai pedal though.

I'd at least like to add an una corda and a sost. pedal, but my MIDI controller (Impakt LX88+) only has one phono jack, being used for the sustain ped.

So if there are MIDI pedals capable of being recognized by Pianoteq, which do you recommend?

I also have a Yamaha S80 which has an available foot controller ped. 1/2 jack. Any recommendations there?