Hi,

Unfortunately, the Neuron Core is created with Elementor standards, and they do not allow to extend directly the elements, we'll look something in the future, but for the moment that's how it is, you need to edit directly on the plugin.

How to add a Custom Post Type.

1) Create the Custom Post Type, via a plugin or manually in the functions.php of the child theme.

// Custom Post Type
function neuron_books_post_type() {
    // Post Type
    $labels = array(
        'name'                  => __('Books', 'neuron-core'),
        'singular_name'         => __('Books Item', 'neuron-core'),
        'menu_name'             => _x('Books', 'admin menu', 'neuron-core'),
        'name_admin_bar'        => _x('Books Item', 'add new on admin bar', 'neuron-core'),
        'add_new'               => __('Add New Item', 'neuron-core'),
        'add_new_item'          => __('Add New Books Item', 'neuron-core'),
        'new_item'              => __('Add New Books Item', 'neuron-core'),
        'edit_item'             => __('Edit Books Item', 'neuron-core'),
        'view_item'             => __('View Item', 'neuron-core'),
        'all_items'             => __('All Books Items', 'neuron-core'),
        'search_items'          => __('Search Books', 'neuron-core'),
        'parent_item_colon'     => __('Parent Books Item:', 'neuron-core'),
        'not_found'             => __('No books items found', 'neuron-core'),
        'not_found_in_trash'    => __('No books items found in trash', 'neuron-core'),
        'filter_items_list'     => __('Filter books items list', 'neuron-core'),
        'items_list_navigation' => __('Books items list navigation', 'neuron-core'),
        'items_list'            => __('Books items list', 'neuron-core')
    );
    $supports = array(
        'title',
        'editor',
        'excerpt',
        'thumbnail',
        'comments',
        'author',
        'custom-fields',
        'revisions',
    );
    $args = array(
        'labels'          => $labels,
        'supports'        => $supports,
        'public'          => true,
        'capability_type' => 'post',
        'rewrite'         => array('slug' => 'books'), // Permalinks format
        'menu_position'   => 5,
        'menu_icon'       => (version_compare( $GLOBALS['wp_version'], '3.8', '>=')) ? 'dashicons-portfolio' : false,
        'has_archive'     => false
    );
    
    register_post_type('books', $args);
}

2) Open the base.php in the neuron-core > includes > posts > base.php.

3) In the base.php add your custom post types in the setting called 'posts_type' which is located in the line 89. http://prntscr.com/nag3kh

4) In the line 2955 of the base.php you need to add your custom post type in the switch as the following screenshot. http://prntscr.com/nag49v

case 'books':
    $neuron_posts_type = 'books';
    $neuron_posts_name = 'blog';
    $neuron_posts_taxonomy = 'category';
    $neuron_posts_normal_query = $settings['posts_query_normal_post'];
    $neuron_posts_metro_query = $settings['posts_query_metro_post'];
    $neuron_posts_wrapper_class = 'l-blog-wrapper';
    $neuron_posts_holder_class = 'l-blog-wrapper__posts-holder l-blog-wrapper__posts-holder--'. $settings['posts_layout_model'] .'';
    $neuron_posts_item_class = 'o-blog-post';
    break;

Feel free to ask for anything you need.

Kind Regards,
NeuronThemes

Simply skip the first step, and start from the second step. In the first step we create a new custom post type, so in your case you have already created.

Feel free to ask for anything you need.

Kind Regards