I know I have seen this before but as it was tough for me to find and I needed a slighlty different sollution will share this again.
Just use Java script as follows in an external event and you can do it once and call it to all your scenes 
document.addEventListener(‘keydown’, function(event) {
if (event.altKey) {
if (event.key === ‘s’) {
event.preventDefault();
}
if (event.key === ‘t’) {
event.preventDefault();
}
}
});