Hook um_get_form_fields

um_get_form_fields.php

<?php

/**
 * Hook: um_get_form_fields
 *
 * Type: filter
 *
 * Description: Extend form fields.
 * Used in the core to prepare form fields.
 *
 * @example https://github.com/ultimatemember/ultimatemember/blob/master/includes/core/class-fields.php#L1524
 * @link    https://docs.ultimatemember.com/article/1143-umgetformfields
 *
 * @package um\core
 * @see     um\core\Fields::get_fields()
 * @see     um_get_form_fields()
 * @since   2.0
 * @version 3.0
 *
 * @param array $fields Form fields.
 *
 * @return array|string An array of fields or empty string if the form is not set.
 */
function my_get_form_fields( $fields ) {
	// your code here.
	return $fields;
}
add_filter( 'um_get_form_fields', 'my_get_form_fields', 100, 1 );