How to add a custom post type into the sub-menu of a custom menu

Yeah I know the title is a bit weird, but it describes the problem that I faced today. I started developing my first real plugin and I wanted to achieve the following: create an admin menu page, with function add_menu_page() ¬†-> easy, add a sub-menu page called “settings”, with function add_submenu_page() -> easy, register¬†a custom […]