It looks like an NVR but the easiest way to tell if the existing switch IS an NVR is to see if it works like one.
Plug the machine in, press start and machine will run.
Unplug it without pressing the stop button first and the machine will stop.
Put the plug back in again without pressing any buttons. If the machine starts by itself, that isn't an NVR switch.
If you have to press the start button to get it running after the break in power caused by pulling and reinserting the plug (the "no volt" situation) then it is a NVR and is doing what it should - preventing an uncontrolled restart after an interruption in the supply.
Assuming it an NVR you can add as many emergency stop buttons and footswitches as you like in series just by running the live wire through them on the way into the NVR switch or between the switched live and the motor. These switches should be a "Normally Closed" aka NC type and have a momentary pushbutton type action.
If you're in the EU, we use brown to indicate the "live" or "L1" wire. If you use mains flex to wire your extra switches in, you use a piece of BROWN tape or brown heatshrink on each end of the blue wire to show that it's being used as a "live".
Also be sure you use a flex that is big enough to carry the motor current. Look at the existing flex - the cross sectional area e.g 1.0mm2 1.5mm? or whatever will probably be embossed into the outer sheath at regular intervals. Use the same or greater.
If you are putting a new switch in a metal box, use a three core wire and earth the box to the body of the machine. If it's in a plastic box, there's no need to take an earth to it and you can wire the extra switch in with two core.
