Metabox Relationship Query Args

Hi, struggling with what to enter in the query args fields of the UI for a relationship. I have a query which works well:

	return [
    'post_type' => 'event',
    'posts_per_page' => '3',
    'orderby'   => 'meta_value',
    'meta_key'  => 'event_date',
    'order'     => 'ASC',
        'meta_query' => array(
            array(
                'key' => 'event_date',
                'compare' => '>=',
                'value' => strtotime(date('Ymd', time()))
              )
          )
];

I can enter thesee as three individual key/value pairs in the UI:

    'orderby'   => 'meta_value',
    'meta_key'  => 'event_date',
    'order'     => 'ASC',

and the sorting of what is returned is correct.

I also need to add these args in so that only future events are returned:

        'meta_query' => array(
            array(
                'key' => 'event_date',
                'compare' => '>=',
                'value' => strtotime(date('Ymd', time()))
              )
          )

how do I do that with query args in the UI? Many thanks.