@barnabynagy I don’t know about Casper specifically, but have you tried using the routes.yaml “order” property?
For example, this is the one I distribute with my Weblog theme:
routes:
collections:
/:
permalink: /{slug}/
template:
- index
order: featured desc, published_at desc
taxonomies:
tag: /tag/{slug}/
author: /author/{slug}/
See: Ghost Themes - Dynamic URLs & Routing
You should be able to search for routes.yaml from your admin panel, download your existing one, make a backup copy, and then try putting this content in and uploading it and see if it does it. If it doesn’t work, revert.