WP Inventory Manager Dashboard Admin Menu

Do you need to add another page for admin purposes under the existing WP Inventory tab?  This action is what you need!

Called when WP Inventory is adding admin menus. Allows you to add sub-menus to the WP Inventory top-level menu, and know that the WP Inventory top-level menu is ready.

add_action('wpim_admin_menu', 'my_custom_function');

function my_custom_function() {
    // Adds a submenu to the WP Inventory menu
    add_submenu_page(WPIMCore::MENU, $page_title, $menu_title, $capability, $menu_slug, $function);

The add_submenu_page is a WordPress function.  You can view the documentation here.