Hiding a page from navigation bar but not making it private?

In your themes header.php file (probably without seeing your theme) you will find code similar to the following:
<?php wp_list_pages(title_li=&depth=1'); ?>
Add an include function to include only the page IDs that you want to show in the navbar, like this:
<?php wp_list_pages(title_li=&depth=1&include=1,2,3,4,5'); ?>
This will only include pages with IDs 1,2,3,4 and 5 in the navbar that lists your pages.

If I add that, and go to the site itself, it says “Unexpected “<” or “?” in header.php on line (Where I put it, 35 or 37.)” It’s not reconizing that line.
Do I take out the existing line, or add this one somewhere else?
Here’s what the existing code looks like:

<?php
			$custom_page_links = wp_list_pages('sort_column=menu_order&depth=1&title_li=&echo=0');

			$custom_page_links = str_replace("<a href", " | <a href", $custom_page_links);

The theme is Afterland. Here’s the site.
https://thehungergamestribute.co.cc/

You can use Exclude Pages ? WordPress Plugins rather than modify theme code.

Well, that was easy. Thanks!