C450104

I think I’ll probably be using this guide to expand the functionality of my custom fields by adding them to the Quick Edit section of my site:
https://shibashake.com/wordpress-theme/expand-the-wordpress-quick-edit-menu

…And I’m just posting this here for posterity’s sake.

Woot! My issue is resolved! Found something that does what I needed:
https://www.ads-software.com/extend/plugins/custom-admin-column/

This came with 2 default new columns that it added to the Posts page that I didn’t really need, but gave me the plugin framework I needed to tweak and add what I wanted.

For anyone coming after me, in the custom_admin_columns.php file, find:

function cac_post_column_filter($columns) {
    $columns['thumbnail'] = 'Featured Image';
    $columns['slug'] = 'Permalink';
    return $columns;
  }
add_filter('manage_post_posts_columns', 'cac_post_column_filter');

After $columns['slug'] = 'Permalink'; Add:
$columns['date_modified'] = 'Date Modified';
Then find:

function cac_column_value($name, $id){
switch($name){
case 'slug':
       $permalink = get_permalink($id);
	echo '<a href="'. $permalink . '" target="_blank">' . $permalink . '</a>';
	break;
case 'thumbnail':
   if(function_exists('get_the_post_thumbnail'))
	echo get_the_post_thumbnail($id, array(75,75));
   break;

After the Thumbnail case, add:

case 'date_modified':
	if(function_exists('the_modified_date'))
		echo the_modified_date();
	break;

Reference: https://codex.www.ads-software.com/Function_Reference/the_modified_date

I also added a few other custom post field columns to my file from using ADV Custom Fields:
https://www.ads-software.com/extend/plugins/advanced-custom-fields/

If anyone ever wants to know how I’ve implemented those, feel free to email me or reply to this post, I’m subscribed.

Ok, so still digging for answers, found this page:

Curtiss Grymala Member Posted 8 months ago
Obviously, you shouldn’t actually modify edit.php, as any changes will be overwritten when you upgrade WordPress.
However, you can try to use the manage_posts_columns filter to add a new column showing the scheduled/published time.

Which lead me to this:
https://scompt.com/blog/archives/2007/10/20/adding-custom-columns-to-the-wordpress-manage-posts-screen

It doesn’t have an example of my specific need, but I’ll keep looking to see if I stumble onto something.

So now at least I know I shouldn’t be messing with the edit.php or any other files like that.