Category tree is flattened inside admin upon saving

Question

Is there a way to avoid WordPress "flattening" the category tree when a child category is selected?

This applies to both custom taxonomies and WP's built in "category" taxonomy.

To explain further, say I have the following category tree:

Parent
    Child
        Grandchild
Another parent
    Another child
    Another child
A third parent

If I then select "Grandchild" as my category, the tree will now look like this upon saving:

Grandchild
Parent
    Child
Another parent
    Another child
    Another child
A third parent

This makes it very hard for authors to remember which grandchild belongs to which parent and imo makes absolutely zero sense. I guess one reason for this might be so that the selected category is always in the top of the list, but I would very much like to disable this behaviour.

Also see attached image.

Please note that this is not theme or plugin-related. I tried this with a completely fresh WP-install with zero plugins and the default theme.

Answer 1

I haven't fully tested this, but it may be helpful: Categories in Hierarchical Order plugin at https://wordpress.org/plugins/categories-in-hierarchical-order/

Answer 2

The plugin can be resumed to this simple code:

add_filter( 'wp_terms_checklist_args', function( $args ) {
    $args['checked_ontop'] = false;
    return $args;
});