I would like to create a custom form with a textfield in which I input some data and it gets saved in the variable table.

The form should only contain the Add, Remove, and Add more button to add additional textfields.

When the textfield is empty, there should be an Add button; when the textfield is not empty, there should be a Remove button.
Clicking on the Add more button should create an empty textfield with an Add button.

All this need to happen without page reload.

I was able to add the Add, Remove, Add more, and Submit buttons.
I looked into the available resources and example modules, but I can’t find helpful resources.

Can anyone help me to modify the code so that the Submit button can be removed?

function mymodule_menu() {
    $items = array();
    $items['admin/mymodule'] = array(
        'title' => t('Example form'),
        'type' => MENU_CALLBACK,
        'page callback' => 'drupal_get_form',
        'page arguments' => array('mymodule_ajax_example_add_more'),
        'access callback' => TRUE,
    );

    return $items;
}

function mymodule_ajax_example_add_more($form, &$form_state) {
  $mymodule_ajax_events = variable_get('mymodule_ajax_example_content', array());
  $mymodule_ajax_events_count = count($mymodule_ajax_events);
  if ($mymodule_ajax_events_count == 0) {
    $mymodule_ajax_events_count = 1;
  }

  $form = array();
  $form['#tree'] = TRUE;
  $form['mymodule_ajax_events'] = [
    '#type' => 'container',
    '#weight' => 80,
    '#tree' => TRUE,
    // Set up the wrapper so that AJAX will be able to replace the fieldset.
    '#prefix' => '<div id="js-ajax-elements-wrapper">',
    '#suffix' => '</div>',
  ];
  $form_state['field_deltas'] = isset($form_state['field_deltas']) ? $form_state['field_deltas'] : range(0, $mymodule_ajax_events_count-1);

  $field_count = $form_state['field_deltas'];
  foreach ($field_count as $delta) {
    $form['mymodule_ajax_events'][$delta] = [
      '#type' => 'container',
      '#attributes' => [
        'class' => ['container-inline'],
      ],
      '#tree' => TRUE,
    ];

    $form['mymodule_ajax_events'][$delta]['event_url'] = [
      '#type' => 'textfield',
      '#title' => t('Event URL' . ($delta + 1)),
      '#size' => 40,
      '#default_value' => (isset($mymodule_ajax_events[$delta])) ? $mymodule_ajax_events[$delta] : '',
    ];

    $form['mymodule_ajax_events'][$delta]['remove_event_url'] = array(
      '#type' => 'submit',
      '#value' => t('Remove'),
      '#submit' => ['mymodule_ajax_example_add_more_remove'],
      '#ajax' => [
        'callback' => 'mymodule_ajax_example_add_more_remove_callback',
        'wrapper' => 'js-ajax-elements-wrapper',
      ],
      '#weight' => 50,
      '#attributes' => [
        'class' => ['button-small'],
      ],
      '#name' => 'remove_event_url_' . $delta,
    );
  }

  $form['mymodule_ajax_events']['add_event_url'] = array(
    '#type' => 'submit',
    '#value' => t('Add one more'),
    '#submit' => ['mymodule_ajax_example_add_more_add_one'],
    '#ajax' => [
      'callback' => 'mymodule_ajax_example_add_more_add_one_callback',
      'wrapper' => 'js-ajax-elements-wrapper',
    ],
    '#weight' => 1,
  );
    $form['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Submit'),
    '#weight' => 100,
  );

  return $form;
}

function mymodule_ajax_example_add_more_remove($form, &$form_state) {
  $delta_remove = $form_state['triggering_element']['#parents'][1];
  $k = array_search($delta_remove, $form_state['field_deltas']);
  unset($form_state['field_deltas'][$k]);

  $form_state['rebuild'] = TRUE;
  drupal_get_messages();
}

function mymodule_ajax_example_add_more_remove_callback($form, &$form_state) {
  return $form['mymodule_ajax_events'];
}

function mymodule_ajax_example_add_more_add_one($form, &$form_state) {
  $form_state['field_deltas'][] = count($form_state['field_deltas']) > 0 ? max($form_state['field_deltas']) + 1 : 0;
  //mymodule_ajax_example_add_more_validate();
  $form_state['rebuild'] = TRUE;
  // drupal_get_messages();
}

function mymodule_ajax_example_add_more_add_one_callback($form, $form_state) {
  return $form['mymodule_ajax_events'];
}

function mymodule_ajax_example_add_more_validate($form, $form_state) {
    dpm($form_state);
  foreach ($form_state['values']['mymodule_ajax_events'] as $key => $item) {
      //dpm($item);
      dpm($item['event_url']);
   if (!empty($item['event_url'])) {
      if (!preg_match('/https://example.com.*/i', $item['event_url'])) {
        form_set_error("mymodule_ajax_events][$key][event_url", 'Enter a valid Event URL.' . ($key + 1));
        //
      }else{
       drupal_set_message('URL ' . ($key + 1) . ' Created' );
   }
  }
 }
}

function mymodule_ajax_example_add_more_submit($form, $form_state) {
  $events_content = array();
  $events_count = 0;
  foreach ($form_state['values']['mymodule_ajax_events'] as $key => $item) {
    if (!empty($item['event_url'])) {
      $events_content[] = $item['event_url'];
      $events_count++;
   }
 }
  variable_set('mymodule_ajax_example_content', $events_content);
  variable_set('mymodule_ajax_example_count', $events_count);
}