AddControlsToAllModules.php

<?php
/**
 * Add custom field option on all modules.
 *
 * @param array $modules
 *
 * @return array
 */
function smpl_extend_modules( $modules ) {
	// Ensure we run this code only once because it's expensive.
	static $is_applied = false;
	if ( $is_applied ) {
		return $modules;
	}
	// Bail early if the modules list empty.
	if ( empty( $modules ) ) {
		return $modules;
	}
	foreach ( $modules as $module_slug => $module ) {
		// Ensure fields list exist.
		if ( ! isset( $module->fields_unprocessed ) ) {
			continue;
		}
		/**
		 * Fields list on the module.
		 *
		 * @var array
		 *
		 * The structures:
		 * array(
		 *     'field_slug' => array(
		 *         'label'       => '',
		 *         'description' => '',
		 *         'type'        => '',
		 *         'toggle_slug' => '',
		 *         'tab_slug'    => '',
		 *     ),
		 *     ... Other fields.
		 * )
		 */
		$fields_list = $module->fields_unprocessed;
		// Add 'Member Field' option on 'Member Toggle' options group.
		if ( ! empty( $fields_list ) ) {
			$fields_list['member_field'] = array(
				'label'           => 'Member Field',
				'description'     => 'Member field option here.',
				'type'            => 'text',
				'toggle_slug'     => 'member_toggle',
				'tab_slug'        => 'custom_css',
			);
			$modules[ $module_slug ]->fields_unprocessed = $fields_list;
		}
	}
	$is_applied = true;
  return $modules;
}
add_filter( 'et_builder_get_parent_modules', 'smpl_extend_modules' );