问如何使HTML表单按钮在屏幕上放置一个用户可以输入文本的下拉式表单列表

EN

document.querySelector('#newEvent').addEventListener('click', function() { // when "add day" clicked:
  let chosenDay = odays.selectedOptions[0].value; // take the selected option from select box
  document.querySelector('#newNote legend').textContent += ' '+chosenDay; // Here i use it as title but you can do what you want
  document.querySelector('#newNote input').removeAttribute('disabled');  // since we disabled it initialy
  document.querySelector('#newNote').removeAttribute('style'); // show input ready for note
});

<form>
  <fieldset>
    <legend>My Calendar</legend>
    <label for='odays'> Open Days: </label>
    <input type='button' id="newEvent" value='Add Day'><br>
    <select id='odays'name='odays'>
      <option value='monday'> Monday </option>
      <option value='tuesday'> Tuesday </option>
      <option value='wednesday'> Wednesday </option>
      <option value='thursday'> Thursday </option>
      <option value='friday'> Friday </option>
      <option value='saturday'> Saturday </option>
      <option value='sunday'> Sunday </option>  
    </select>
  </fieldset>
  <fieldset id="newNote" style="display: none;">
    <legend>Note For</legend>
    <input type="text" placeholder="add some text" disabled>
    <button type="submit">Submit</button>
  </fieldset>
</form>

let daysPlan = "";

function updateMyday() {
  var selectBox = document.getElementById("odays");
  var div = document.getElementById("daysUp");
  //var selectOption = selectBox.options[selectBox.selectedIndex];
  var selectedValue = selectBox.options[selectBox.selectedIndex].value;

  event = window.prompt("what's up that day ?");

  // to show on the page somewhere 
  var newDay = document.createElement("div");
  newDay.textContent = selectedValue + " : " + event;
  div.appendChild(newDay);
  // end show 

  // store it , a variable, a localstorge, else ?
  daysPlan += selectedValue + " : " + event + "\n"
  console.log(daysPlan) // to use and send once submitting 
}

#odays {
  display: none;/* not sure i understood that part*/
}

form {
  float: left;
}

#daysUp {
  white-space: pre;
}

<form><label for='odays'> Open Days: </label><br>

  <input type='button' onclick='let e =document.getElementById("odays"); e.style.display="block";' value='Add Day'><br>

  <select id='odays' name='odays' onchange="updateMyday()">
    <option>Choose a day </option>
    <option value='monday   '> Monday </option>
    <option value='tuesday  '> Tuesday </option>
    <option value='wednesday'> Wednesday </option>
    <option value='thursday '> Thursday </option>
    <option value='friday   '> Friday </option>
    <option value='saturday '> Saturday </option>
    <option value='sunday   '> Sunday </option>
  </select>
</form>
<div id="daysUp">
</div>