src/controller/admin/page/class-custom-rating.php
public function set_submenu() {

		$submenu = Module::CustomRatingGrifus()->getOption( 'submenu' );

		WP_Menu::add(
			'submenu',
			$submenu['custom-rating-grifus'],
			[ $this, 'render' ],
			[ $this, 'add_scripts' ],
			[ $this, 'add_styles' ]
		);
	}
public function set_submenu() {

		$submenu = Module::CustomRatingGrifus()->getOption( 'submenu' );

		WP_Menu::add(
			'submenu',
			$submenu['custom-rating-grifus'],
			[ $this, 'render' ],
			[ $this, 'add_scripts' ],
			[ $this, 'add_styles' ]
		);
	}
Add submenu for this page.

@uses add_submenu_page() → add a submenu page