If your custom post type isn’t showing up in the menu, it might be because you are using camelCase for the post_type parameter. Like I was, efficiently saving myself from underscores and dashes for half an hour. And that is how I learned:
Custom post types names can’t have capital letters! Same goes for taxonomies. Maybe it needs to be in slug form in case you don’t define the rewrite/slug parameter? Maybe. These are the rules, they seem to work:
<?php register_post_type( $post_type, $args ) ?>
$post_type (string) (required) Post type. (max. 20 characters, can not contain capital letters or spaces)
<?php register_taxonomy($taxonomy, $object_type, $args); ?>
$taxonomy (string) (required) The name of the taxonomy. Name should be in slug form (must not contain capital letters or spaces).