Custom Sort Collections Liquid

[trinkermedia]

I have a page which shows all my collections... But the Sort is currently default and I want to have a custom Sort. For that reason I added a Custom Meta Object Field with the name "sorting" and there I add Letters like a, b, c,... ... y, z and I want to sort it that way. How can I sort it?

When I sort a Meta Object List, I can use 

{% assign sorted_headings = shop.metaobjects.heading.values | sort: 'sorting' %}

But this code does not work with collections (of course I changed everything)

[Small_Task_Help]

Hi,

Need to do testing in the backend with code. If you want then you can contact me, details given in signature