Hi Pete – great question!
I do need to highlight first of all that this is very much custom-coding territory and while I’ll be happy to point you in the right direction if I can, it’s ultimately something you’ll need to drive to completion under your own steam 🙂
Our attendee screen uses a regular WordPress list table and these are fairly easy to work with and customize. Here’s some example code (which you could add to a custom plugin – preferred – or else to your theme’s functions.php file) for adding extra columns and populating them:
https://gist.github.com/barryhughes/f7a7b98c374e1c2ba5bb12c922d91264
In your case of course you are probably going to want to figure out the order ID in order to obtain order-specific data for your extra column. In the second callback (in my above snippet) you could make use of $item for this purpose.
Thankfully, $item will be an array and you can access the order ID as follows:
$order_id = $item['order_id'];
I hope that helps and good luck with the customization 🙂