In this tutorial I explain how you can create a list of content based on the content's GRANDPARENT category (not parent) ie:
- Fruit <-- PARENT 
- - Apples <-- CONTENT 
- - Bananas <-- CONTENT 
- Vegetables <-- PARENT 
- - Peas <-- CONTENT 
- - Potatoes <-- CONTENT <br>

Food is a GRANDPARENT category, 

Fruit and Vegetables are Parent Categories, and

Apples, Bananas, Peas and Potatoes are the content.

So... To have a food menu item that lists all content within the categories Fruit and Vegetables do this:

Create your Search and list type based on the content type you wish to list, 
I will pretend it is called Food Types (#__cck_store_form_food_types)
Add a <a href="http://www.seblod.com/store/extensions/922" target="_blank">Search Join</a> field and enter in Join(1) from left to right: 
 #__categories | id | catid | #__content | | 
(the last columun does something, maybe AND or OR, not sure) 
(this field actually reads from right to left - the query is based on article object, so it knows the #__content table already) 
Save and close this field
Add a text field, this field will reference the parent_id of a category.
Call it something like: Category Parent Id (category_parent_id).
Storage: Standard | Category | parent_id
As a final touch, add a search button to your search form, so that you can search from the front end.
Then in the List View, add some fields ie Article Title, Introtext etc
Save this Search & List type.
Next, create a Menu Item: Seblod List.
Select the List & Search type just created, and here comes the crucial bit:
In the Overrides (Live/Variation) tab, enter the value of the GRANDPARENT category.
Save and close

On the front end you should be able to see the list of articles.


This took me A LONG time to figure out, I never thought it would be this simple!!

I used

Joomla 3.5.1

Seblod 3.8.0