I have this code in my custom walker
( ! empty ( $item->description ) && 0 == $depth ) ? ' <span class="desc">' . $item->description . '</span>' : '';
And enabled the descriptions, now for posts WordPress fills in the entire post content into that field in the admin. Why is that? For categories it fills in the category description, that makes more sense but I still not really get the intend of this, I mean I like to use this for menu subtitles and not long texts?
Can I prevent WordPress from pulling some default values into this field after I import stuff (only way I tested) or should I code more to have a new custom field in there called "subtitle" with only a text input not a textarea. I have looked into it and it requires a lot if code and I like to stay minimal. The description just works with some simple worker change.