// Showing post with meta key filter in Portfolio Widget
add_action( 'elementor/query/my_custom_filter', function( $query ) {
    // Get current meta Query
    $meta_query = $query->get( 'meta_query' );
    // Append our meta query
    $meta_query[] = [
        'key' => 'project_type',
        'value' => [ 'design', 'development' ],
        'compare' => 'in',
    ];
    $query->set( 'meta_query', $meta_query );
} );