Hi,

You will have to write some custom code.

In your theme functions.php file add following code at the bottom:

add_action('wp_footer', function() {
    ?>
    <script type="text/javascript">
        (function ($) {
            if (typeof $.stecExtend !== 'function') {
                return;
            }
            $.stecExtend(function (m) {
                var filter = [];
                if (m.glob.options.organizer) {
                    $.each(m.calData.eventsPool, function () {
                        var event = this;
                        if (this.organizers.length > 0) {
                            $.each(this.organizers, function(){
                                if (this.name === m.glob.options.organizer) {
                                   filter.push(event);
                                }
                            });
                        }
                    });
                    
                     m.calData.eventsPool = filter;
                }
            }, 'onAddToEventsPool');
        })(jQuery);
    </script>
    <?php
});

Then in your shortcode add organizer attribute and insert the organizer name (case sensitive). 

Example:

[stachethemes_ec organizer="John Doe"]

It should display only events with this organizer.

Replace agenda_get_n with grid_per_click:

[stachethemes_ec organizer="Babytwins" grid_per_click=4] 

Have you included the code I've sent you earlier in your theme functions.php file at the bottom because I don't see it on your page?