WordPress TinyMCE Editor Adding Custom Buttons + Enabling Hidden Buttons

admin-functions.php

<?php
//---------------------------------------------------------------
/**
 * Registers an editor stylesheet for the theme.
 */
function custom_theme_add_editor_styles() {
  add_editor_style( 'editor-style.css' );
}
add_action( 'admin_init', 'custom_theme_add_editor_styles' );
//---------------------------------------------------------------
/**
 * Callback function to insert 'styleselect' into the $buttons array
 * The filter mce_buttons_2 refers to the second row of buttons in the editor
 * where mce_buttons = first row and mce_buttons_3 = third row.
 */
function custom_enable_mce_styleselect( $buttons ) {
  array_unshift( $buttons, 'styleselect' );
  return $buttons;
}
add_filter( 'mce_buttons_2', 'custom_enable_mce_styleselect' );
//---------------------------------------------------------------
/**
 * Callback function to filter the MCE settings
 */
function custom_mce_before_init_insert_formats( $init_array ) {
  // Define the style_formats array
  $style_formats = array(
    // Each array child is a format with it's own settings
    array(
      'title' => 'Shows',
      'items' => array(
        array(
          'title' => 'Title',
          'inline' => 'span',
          'classes' => 'format-title',
          'exact' => true,
          ),
        array(
          'title' => 'Subtitle',
          'inline' => 'span',
          'classes' => 'format-subtitle',
          'exact' => true,
          ),
        array(
          'title' => 'Presents',
          'inline' => 'span',
          'classes' => 'format-presents',
          'exact' => true,
          ),
        array(
          'title' => 'Byline',
          'inline' => 'span',
          'classes' => 'format-byline',
          'exact' => true,
          ),
        array(
          'title' => 'Dates',
          'inline' => 'span',
          'classes' => 'format-dates',
          'exact' => true,
          )
        )
      )
    );
  // Insert the array, JSON ENCODED, into 'style_formats'
  $init_array['style_formats'] = json_encode( $style_formats );

  return $init_array;

}
// Attach callback to 'tiny_mce_before_init'
add_filter( 'tiny_mce_before_init', 'custom_mce_before_init_insert_formats' );
//---------------------------------------------------------------
/**
 * Create an init process for registering our button(s).
 */
add_action('init', 'custom_tinymce_shortcode_button_init');
function custom_tinymce_shortcode_button_init() {
  //Add a callback to regiser our tinymce plugin
  add_filter( 'mce_external_plugins', 'custom_tinymce_register_plugins' );

  // Add a callback to add our button to the TinyMCE toolbar
  add_filter( 'mce_buttons', 'custom_tinymce_register_buttons' );
  add_filter( 'mce_buttons_3', 'custom_tinymce_register_buttons_3' );
}
/**
 * Adding an existing hidden button to the first row.
 */
function custom_tinymce_register_buttons( $buttons ) {
 array_push( $buttons, 'table' );
 return $buttons;
}
/**
 * Adding a custom button to the third row.
 */
function custom_tinymce_register_buttons_3( $buttons ) {
 array_push( $buttons, 'custom_flexvideo' );
 return $buttons;
}
/**
 * Register the JS files that control the operation of the new buttons.
 */
function custom_tinymce_register_plugins( $plugin_array ) {
 $plugin_array['table'] = get_stylesheet_directory_uri().'/includes/tinymce/plugins/table/plugin.min.js';
 $plugin_array['custom_flexvideo'] = get_stylesheet_directory_uri().'/includes/tinymce/plugins/custom-shortcodes/flexvideo.js';
 return $plugin_array;
}
//---------------------------------------------------------------

flexvideo_plugin.js

jQuery(document).ready(function($) {

    tinymce.create('tinymce.plugins.custom_flexvideo_plugin', {
        init : function(ed, url) {
                // Register command for when button is clicked
                ed.addCommand('custom_flexvideo_insert_shortcode', function() {
                    selected = tinyMCE.activeEditor.selection.getContent();

                    if( selected ){
                        // If text is selected when button is clicked
                        // Wrap shortcode around it.
                        content =  '[flexvideo aspect="widescreen" platform="youtube"]'+selected+'[/flexvideo]';
                    }else{
                        content =  '[flexvideo aspect="widescreen" platform="youtube"]paste_embed_code_here[/flexvideo]';
                    }

                    tinymce.execCommand('mceInsertContent', false, content);
                });

            // Register buttons - trigger above command when clicked
            ed.addButton('custom_flexvideo', {
                title : 'Insert Flexvideo Shortcode',
                cmd : 'custom_flexvideo_insert_shortcode',
                image: url + '/icons/icon-flexvideo.svg' });
        },
    });

    // Register our TinyMCE plugin
    // first parameter is the button ID1
    // second parameter must match the first parameter of the tinymce.create() function above
    tinymce.PluginManager.add('custom_flexvideo', tinymce.plugins.custom_flexvideo_plugin);
});