I am trying to filter child drop-down inputs based on parent dropdown. For example, if I select a state I need to show the cities only in the selected state.
What I have done so far is added this below function in the functions.php file.

function getCities() {
//get the value from the 'parent' field, sent via the AJAX post.
$choice = $_POST['choose_mavatam1'];

  switch($choice) {
    case "Tamilnadu":
      $cities = [
        "Chennai" =>"Chennai",

      ];
      break;
    case "Karnataka":
      $cities = [
        "Bangalore"=>"Bangalore",

      ];
      break;
    default:
      //code to do something if other options are not selected (throw an error, or set $cities to a default array)
      $cities = ["no city"];

  }
return $cities;
}

I called this below function in Choices Callback field of ultimate member plugin for the parent field. The bug I face is the Edit Choices becomes this switch case’s default value automatically as no city when I used this callback function.