SoulOnFire

Okay, I have managed to go so far using the information from the Codex:
1) I have added the plugin and the button

<?php
/*
Plugin Name: TinyMCE Template Plugin
*/

/* Add the TinyMCE Template Plugin */
add_filter('mce_external_plugins', 'my_custom_plugins');

function my_custom_plugins () {
     $plugins = array('template'); //Add any more plugins you want to load here
     $plugins_array = array();

     //Build the response - the key is the plugin name, value is the URL to the plugin JS
     foreach ($plugins as $plugin ) {
          $plugins_array[ $plugin ] = plugins_url('tinymce/plugins/', __FILE__) . $plugin . '/plugin.min.js';
     }
     return $plugins_array;
}

function myplugin_tinymce_buttons($buttons)
 {
      //Add style selector to the beginning of the toolbar
      array_unshift($buttons, 'template');

      return $buttons;
 }
add_filter('mce_buttons','myplugin_tinymce_buttons');
?>

2) I have set up a template file and the following code:

tinymce.init({
    plugins: "template",
    toolbar: "template",
    templates : "/templates/templates.php"
});

However, now I have the following error with the plugin.min.js file:
‘TypeError: e.notificationManager is undefined’

I am going out of my mind with this and I have no idea what I am doing wrong. Am I missing something? Any help will be appreciated.

Okay, I just found out more information. As it turns out the problem is that some products are part of several categories. A product is shown only in one category. I can’t figure out how the category is chosen.

So for example if I have a chair in both ‘work chairs’ and in ‘management chairs’, it will be shown only in work chairs. The answer might be pretty obvious but I am still fairly new to programming and to WordPress and I can’t figure it out.