Getting the available template variables in a custom module
According to your code, you are creating a custom template for a paragraph.

As you are trying to access variables, that will be added by the paragraph module, you'll have to tell the theming system that it is a paragraph.

You can do so by adding the 'paragraph' base hook. This way the template will get the variables provided by the paragraph (pre-)processing:

/**
 * Implements hook_theme()
 */
function episode_data_theme($existing, $type, $theme, $path) {
  return [
    'paragraph__episode_content_question_slider' =&gt; [
      'base hook' =&gt; 'paragraph',
    ],
  ];
}