Multiple custom post types under one admin menu

I’m not sure where to start with this one.

I want to have 4 custom post types (Gigs, Venues, Holidays and Potentials) listed under a main heading of Events Manager, but don’t want Events Manager to be a custom post type.

Thanks in advance to anyone who can help.

Just create a “placeholder” menu that you can then assign all your post types to:

function wpse_226690_admin_menu() {
    add_menu_page(
        'Events Manager',
        'Events Manager',
        'read',
        'events-manager',
        '', // Callback, leave empty
        'dashicons-calendar',
        1 // Position
    );
}

add_action( 'admin_menu', 'wpse_226690_admin_menu' );

And then in your register_post_type calls:

'show_in_menu' => 'events-manager',

Tada!