Adding admin link to Appearance via admin_menu, adds link to theme details modal

Question

That’s not how you add submenus to the appearance menu, or how you create settings pages for themes.

Adding a submenu involves either add_submenu_page which lets you add submenus to any menu item, or the helper function add_theme_page which is for the appearance menu.

Here’s one of the examples from the official documentation:

function add_test_theme_page() {
    add_theme_page( 'Theme Title Settings', 'Theme Menu Settings', 'edit_theme_options', 'test-theme-options', 'theme_option_page' );
}
add_action( 'admin_menu', 'add_test_theme_page' );

function theme_option_page() {
    echo 'This is a test theme options page!';
}