WordPress Customize Section site identity, menus, widgets and static front page

Question

I want to know is there a way to customize wordpress out of the box customize options (site identity, menus, widgets and static front page). I know how to add more sections to customize side bar but is there any way to edit the out of the box option (site identity, menus, widgets and static front page). I want to add a new control to site identity section but in functions.php I was unable to find where it was being declared

Answer 1

I found where these sections are being declared and can be edit. They are not in functions.php file because this file is for us to add more functionality the out of the box options are in a file named
class-wp-customize-manager.php . This file is not located in theme directory but instead it is located in wp-includes folder.