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I think the filter should be:

$query->set( 'orderby', 'meta_value' );
$query->set( 'meta_key', 'mm_fornavn' );
$query->set( 'order', 'ASC' );

For more info about the params, please read the Codex about WP_Query class.

Hi,

For custom column that you created, you must specify the way to query the data to sort them. You might want to add a hook to pre_get_posts in the class constructor and then filter the query, like this:

class Prefix_Custom_Admin_Columns extends MB_Admin_Columns_Post {
    function __construct() {
        parent::__construct();
        add_action( 'pre_get_posts', array( $this, 'filter' ) );
    }
    // Other methods
    function filter( $query ) {
        // Sample code to sort the data
        $query->set( 'orderby', 'post_date' );
        $query->set( 'order', 'ASC' );
    }
}

Ok, no problem. It's done.

Just add 'std' => 'no' to the field 😉

Currently you can do that with 'max_file_upload' => 1 for image_advanced field 🙂

How to you want your pagination to be?

Yes, that would work, too. I'm refactoring the code to make it better 🙂

Ah, sorry, for image fields, the returned value is always an array. You need to change the code to:

$object_imgs = isset( $sector['rw_sector-object-image'] ) ? $sector['rw_sector-object-image'] : array();
if ( ! empty( $object_imgs ) ) {
    foreach ( $object_imgs as $object_img ) {
        echo '<div class="sector-object-img">
            <div class="slider slider-for">
            <img src="' . wp_get_attachment_image_url( $object_img, 'type=image_advanced&size=full&multiple=true' ) . '">
        </div>
        </div>';
    }
}