script.js

(function ($) {
    "use strict";
    $(function() {
      
      $('.more .more-trigger').on('click', function(e) {
            var $this = $(this),
                text = $this.hasClass('open') ? 'more' : 'less';

            $this
                .text( text )
                .toggleClass('open')
                .closest('.more')
                .find('.more-content')
                .stop()
                .slideToggle(300);
        });
      
    });
}(jQuery));

shortcode.php

add_shortcode( 'more', 'moreShortcode' );

function moreShortcode( $atts, $content ) {
  ob_start();
  ?>
  <div class="more">
    <div class="more-content" style="display:none;">
      <?= $content ?>
    </div>
    <div class="more-line">
      <div class="more-trigger">more</div>
    </div>
  </div>
  <?php
  return ob_get_clean();
}