hypeDocument.getElementById("Button-Play").style.visibility = "hidden";
"Button-Play" is a unique element ID that you've assigned in Identity Inspector. This JS could be assigned to this button itself, or through another script. It not only makes the button visually disappear, but also keeps it from being clickable.
If you ever need this reversed and need to show that button again, you would use:
hypeDocument.getElementById("Button-Play").style.visibility = "visible";
I use this all the time with my Hype projects; works like a charm.