https://www.pbainbridge.co.uk/2023/12/check-for-existing-form-submit-triggers.html

Check for existing Form Submit Triggers.gs

function checkTriggers() {

  // get active spreadsheet
  var ss = SpreadsheetApp.getActiveSpreadsheet();

  // get all existing Triggers
  var triggers = ScriptApp.getUserTriggers(ss);


  // loop through each Trigger
  for (var i = 0; i < triggers.length; i++) {

    // get a single Trigger
    var trigger = triggers[i];

    // get Trigger event type
    var triggerEventType = trigger.getEventType();

    // check if onFormSubmit event type
    if (triggerEventType == ScriptApp.EventType.ON_FORM_SUBMIT) {

      console.log("An existing onFormSubmit trigger has been detected - now deleting");

      // delete existing Trigger
      ScriptApp.deleteTrigger(trigger);

    } else {
      console.log("No existing onFormSubmit trigger has been detected");
    };

  };


  // create new onFormSubmit Trigger
  ScriptApp.newTrigger('YOUR FUNCTION NAME HERE')
    .forSpreadsheet(SpreadsheetApp.getActive())
    .onFormSubmit()
    .create();
  console.log('New Form trigger successfully created');

  console.log('You are good to go!');

}