Replace page links with "page x of y" for multi page posts

Take a look at the source for get_next_posts_link() in wp-includes/link-template.php. Note how the pagination data is stored in globals.

I recently discovered a very helpful hack that allows having both next and prev text (which I replaced with arrows) and a list of linked pages in between the arrows

start by linking to the source of that ‘hack’ to give anybody here a reference point to build on.

in general, in a multi-page post (or page) – done with <!--nextpage--> – within the loop, the current page is the global variable $page and the total number is $numpages

Here’s the link to the customization:
https://www.velvetblues.com/web-development-blog/wordpress-number-next-previous-links-wp_link_pages/

While adding the customization to the site I’m working on, I did figure out that the variables I want to use are the $page and $numpages – my question then is where in the template do I change out producing the string of page links with the “Page $page of $numpages” code.

here’s an example page of what I’m working on:
https://blog.insidebeautiful.com/?p=56&page=2

I don’t see any easy way to integrate your idea into wp_link_pages() by just using filter functions;
you possibly need to write your own function to replace wp_link_pages()

btw: as reference, the core function wp_link_pages() is in /wp-includes/post-template.php from line 637