Is it possible to add a custom field to an existing “widget” in the backend?
What I wanna do is provide a way to have a checkbox to apply a thumbnail that is double the size of the normal one on the frontend. So I’m thinking of simply adding a custom field as a checkbox that says “Double the size” and when checked I return a different output on the frontend.
That is not the problem, I know how to do so.
However I wonder if it possible to locate this checkbox in the post-thumbnail widget in the backend?
Normally when adding a custom field it appears underneath the excerpt or content area. Is it possible to locate this checkbox inside the post-thumbnail widget?
Thank you in advance
Just filter
admin_post_thumbnail_html
and append your checkbox HTML: