Sorry, try this:
'show_ui' => false,
'menu_position' => 'edit.php?post_type=main_posttype or registered section'
For example if you want it under Themes it would be:
'menu_position' => 'themes.php'
This on your post type registering.
Sorry, try this:
'show_ui' => false,
'menu_position' => 'edit.php?post_type=main_posttype or registered section'
For example if you want it under Themes it would be:
'menu_position' => 'themes.php'
This on your post type registering.