You can write this in display business rule and then set them mandatory to false in your onload client script

var mandatory_fields=[];

var set = new GlideappVariablePoolQuestionSet();

  set.setRequestID('put your request item sys_id');

  set.load();

  var vs = set.getFlatQuestions();

  for (var i = 0; i < vs.size(); i++) {

if(vs.get(i).mandatory==true){

mandatory_feilds.push(vs.get(i).getName());

}

  }

g_scratchpad.mandataoryArray=mandatory_fields;

In your client script use this

for (i=0; i<g_scratchpad.mandatoryArray.length;i++){

g_form.setMandataory(g_scratchpad.mandatoryArray[i],false);

}