The walker class is setup to deal with one level at a time. If I’m understanding your illustrations correctly, you are trying to go with the nth element of every level at a time. The first level below 1 being 1.1, 1.2, 1.3, etc. The level below 1.2 would be 1.2.1, 1.2.2, 1.2.3, etc. Every element in a level would have the same parent. If you want any other organization than one level at a time, you either need to restructure your data or create a different sort of walk method.
The base walker loops through all elements of a level before recursing to the next. You need one that recurses at every element. You can still extend Walker_Nav_Menu, but override the base Walker::walk() method to alter the underlying logic.
Sorry for replying late.
Yes, I’m trying to create a custom walker with different logic when traversing through all elements. I have another question but I think I might create another topic for this. I need to determine if the element is the last child of the current parent element.
Okay, so I solved my problem using this link: https://wordpress.stackexchange.com/a/49005/91164 The example only shows how to add classes to the last child of its siblings. But want I want to do is to modify how the last child displays.
Though this is the closest to what I’m looking for, I just had to modify some logics of this code.
I also encountered some problems displaying the item title. What I did was, instead of using $item, I used $element in function display_element(). For example (retrieving the item’s url): $element->url instead of $item->url.
