Eintrag in die functions.php

/*keep flexible content blocks closed */

function my_acf_admin_head() {
?>
<script type="text/javascript">
(function($){

$(document).ready(function(){

$( ".-collapse" ).each(function( index ) {
$( this ).click();
});

});

})(jQuery);
</script>
<?php
}

add_action('acf/input/admin_head', 'my_acf_admin_head');