Hi Eduardo, sorry for being late to answer ??
Well the goal of this custom field is to call a thumbnail which is linked to a page just in case it’s called on the home page for instance.
It’s useful when my friends that are using the website want to feature on the homepage a page which already has a featured image.
Example: a page about pigs with a photo of pigs, but if they feature it on the homepage, the image used is a cat.
For this hook, I’ve seen it with Meteor slider, you can past a template in your child folder and it helps customizing the plugin.
For instance, I’ll soon have to limit the number of characters called for the excerpt:)
