How to sort posts in admin by titles with dd.mm.yyyy format?

It looks like the post titles have the date format DD.MM.YYYY.

We can order the DD.MM.YYYY titles as YYYYMMDD with:

$query = new WP_Query( [ 'orderby' => 'wpse_mod_title ' ] );

that’s supported with this kind of plugin:

/**
 * Plugin Name: WPSE-274981: Sort DD.MM.YYYY Post Titles as YYYYMMDD In WP_Query 
 * Desription:  Supported by the wpse_mod_title orderby value
 */
add_filter( 'posts_orderby', function( $orderby, \WP_Query $q ) use ( &$wpdb )
{
    $_orderby = $q->get( 'orderby' );
    $_order   = $q->get( 'order' );

    if( 'wpse_mod_title' === $_orderby && in_array( $_order , [ 'ASC', 'DESC' ], true ) )
        $orderby = " CONCAT(
            SUBSTRING( {$wpdb->posts}.post_title, 7, 4 ), // Get the YYYY part
            SUBSTRING( {$wpdb->posts}.post_title, 4, 2 ), // Get the MM part
            SUBSTRING( {$wpdb->posts}.post_title, 1, 2 )  // Get the DD part
        ) {$_order} ";

    return $orderby; 
}, 10, 2 );

Note that this assumes the strict DD.MM.YYYY title format, without spaces.

We might consider trimming it in SQL to make it more flexible.

I think I’m under the influence of @bonger or @thedeadmedic to write this kind of substring ordering. 😉

But consider another approaches first, like writing the titles in a sortable way, in the first place.