Update of custom field removing html code

Gravity Forms has a filter which lets you specify which HTML tags get stripped out here: https://www.gravityhelp.com/documentation/article/gform_allowable_tags/

Adding <table> and the other table related tags, <td> etc. to the above allowable tags filter like below should be enough.

add_filter( 'gform_allowable_tags', 'om_allow_basic_tags', 10, 3 );
function om_allow_basic_tags( $allowable_tags ) {
	return '<p><a><strong><em><table><tbody><tr><th><td>';
}

However, the input also gets run through the wordpress wp_kses_post() function, which in my case was removing my iframe markup even though I had allowed iframes in the above filter. I ended up having to also add iframe to the allowed tags for the wp_kses function by doing the following:

add_filter('wp_kses_allowed_html', 'om_allow_iframes');
function om_allow_iframes( $allowedtags ) {
	$allowedtags['iframe'] = array(
		'src'             => array(),
		'height'          => array(),
		'width'           => array(),
		'frameborder'     => array(),
		'allowfullscreen' => array(),
	);

	return $allowedtags;
}

You might have to do the same for the table tags, not sure.