Edit Entry: Change the action of the Cancel button to close the lightbox

gk_cancel_close_lightbox.php

<?php // DO NOT COPY THIS LINE

function custom_cancel_onclick_js( $back_link, $form, $entry, $view_id, $update_count ) {
	$run_on_views = [2334]; //Change this to the IDs of the Views you'd like to run this filter [100,200,300,...]
	if( in_array( $view_id, $run_on_views ) ){
		return 'window.parent.postMessage({closeFancybox: true}, "*"); return false;';
	}
}
add_filter( 'gravityview/edit_entry/cancel_onclick', 'custom_cancel_onclick_js', 100, 5 );