Section Subnav on Single/Posts ‘Pages’

I’ve got a sub navigation area on my site with code that uses conditional statements to display a section title for the level 1 category/page and follows it with a list of all the level 1’s subcategories/subpages.

This title and list change when the section changes. So, if you’re in Book Reviews the subnav has a ‘Book Reviews’ title and subcategories list and if you’re in Rants the subnav has a ‘Rants’ title and subcategories list. It works the same on my Pages.

HOWEVER, my big problem is that I can not get this to work on the singles/posts. I CAN get WordPress to list a single section’s subcategories on ALL the post ‘pages’. I just can’t get any conditional statements to work so that a book review shows JUST the Book Reviews subnav and a rant has just the Rants subnav.

I’m frustrated as all-get-out.

My site, for reference, is https://www.morevikings.com

The code I can get to work is:

echo "<ul>";
wp_list_categories('orderby=name&hide_empty=0&child_of=1&title_li=<h2>Book Reviews</h2>');
echo "</ul>";

I have this difficulty whether I try conditional statements for this in sidebar.php or in single.php

I’ve tried using is_single, in_category, is_category, etc.

This is a theme I created and am developing.

The following is the subnav code that is working on the Category and Page ‘pages’. It’s clunky but all I can get to work:

<?php
//
if (is_home()) {
        // show a list of all top-level categories on home page
             echo "<ul>";
             wp_list_pages('orderby=name&child_of=111&title_li=<h2>More About moreVikings</h2>');
			 echo "</ul>";
// subnav for categories sections
} elseif (is_category()) {
        // test if it's in the Book Review section and display a title and subcategories list
        if (is_category(array(1,17,18,19,20,21,22,23,24,25,30,31,32,33,34,35,36))) {
             echo "<ul>";
             wp_list_categories('orderby=name&hide_empty=0&child_of=1&title_li=<h2>Book Reviews</h2>');
             echo "</ul>";
        // test if it's in the Rects and Rants section and display a title and subcategories list
         } elseif (is_category(array(41,42,43))) {
              echo "<ul>";
             wp_list_categories('orderby=name&hide_empty=0&child_of=41&title_li=<h2>Book Recs and Rants</h2>');
             echo "</ul>";
        } else {
              // catch-all for other categories
              echo "&nbsp;";
        }
// subnav for pages
} elseif (is_page()) {
        // test if it's in the About section and display a title and subcategories list
        if (is_page(array(2,4,5,6,7,111))) {
             echo "<ul>";
             wp_list_pages('orderby=name&child_of=2&title_li=<h2>About moreVikings</h2>');
			 echo "</ul>";
        } else {
              // catch-all for other pages
              echo "&nbsp;";
        }
} else {
        // catch-all for everything else (archives, searches, 404s, etc)
        echo "&nbsp;";
}
?>