Actually, all I was hoping for was which file to override, and how to call a custom field value to that file. But I figured out a way to develop what I needed.
So, for the benefit of Joomshaper and its community... I wanted to call a custom value to articles in a blog-layout view so as to target them specifically by an HTML ID. Simply calling the article alias and adding it as an HTML ID attribute value worked...
Override: /templates/[JOOMSHAPER_TEMPLATE/html/com_content/blog_item.php (Helix template and native Joomla file for the override)
Just after <div class="item-content">
added: <a id="<?php echo htmlspecialchars($this->item->alias); ?>" aria-hidden="true"></a>
Which, minus my HTML comments regarding customization, renders:
<div class="item-content">
<a id="[ARTICLE-ALIAS]" aria-hidden="true"></a>
Wrap that whole thing in a div with a class for styling:
<div class="item-content">
<div class="article-id">
<a id="[ARTICLE-ALIAS]" aria-hidden="true"></a>
</div>
Any issues with this approach, happy to know. :)