// 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 );
} );