onway

I made it, but not sure if it is the best way. I placed the category dropdown in events-manager/forms/location-editor.php just like in categories-public.php
Then I made AJAX post to save categories when selected.

<script type="text/javascript">
	jQuery(document).ready(function(){
		jQuery('#loc-categoryselect').blur(function(){
			var cats =  jQuery(this).val();
			jQuery.ajax({
				type: "POST",
				url: "<?php echo get_template_directory_uri()?>/plugins/events-manager/forms/location/ajax-save-cats.php",
				data: {
					categories: cats,
					current_location: <?php echo $EM_Location->post_id;?>
				},
				success: function (isError) { //show little green tick
                     	if (!isError){
                     		jQuery('#loc-cat-title').fadeIn('slow').fadeOut(5000);
                     	}
                    }
			});
		});
	});

</script>

The ajax-save-cats.php file use wp_set_object_terms to save the categories.

if (isset($_POST["categories"]) && !empty($_POST["categories"])) {
		$cat_ids = $_POST["categories"];
		$cat_ids = array_map( "intval", $cat_ids );
		$cat_ids = array_unique( $cat_ids );
		$term_taxonomy_ids = wp_set_object_terms( $current_location_id, $cat_ids, "location_category");

		header( "Content-Type: application/json" );
		echo json_encode(is_wp_error( $term_taxonomy_ids ));
	}

I hope it will be fixed in the next update. ??

Im interested in too. How can I Contact you