Thankfully, as with almost everything in WordPress, as soon as I realized I had a problem, I was able to find someone who had already solved it for me. The Exclude Pages Plugin by Simon Wheatley adds a convenient little checkbox to the Page Edit page, asking if you want to include this page in page menus.

Fantastic.

Changing the Default Setting on the Exclude Pages Plugin

Most of the time when I’m using this plugin, it’s because I have some particular small group of pages I want displayed in navigation menus. I want the default to be “DO NOT include this page.” This makes me (and my clients who like to add pages and pages and ruin my beautiful navigation bars) have to think less.

Unfortunately, the default setting for the Exclude Pages plugin is “YES, include this page.” I wanted to change that.

If you’re using the Exclude Pages Plugin, and want to make the default setting an unchecked box, go into the exclude_pages.php file. (I did this right from the Plugin Editor inside the WordPress admin area.) Find the function called “ep_this_page_included” and change the first “return true” to “return false.”

Here’s what it looks like in the code:

BEFORE:

function ep_this_page_included()
{
	global $post_ID;
	// New post? Must be included then.
	if ( ! $post_ID ) return true;
	$excluded_ids = ep_get_excluded_ids();
	// If there's no exclusion array, we can return true
	if ( empty($excluded_ids) ) return true;
	// Check if our page is in the exclusion array
	// The bang (!) reverses the polarity [1] of the boolean
	return ! in_array( $post_ID, $excluded_ids );
	// fn1. (of the neutron flow, ahem)
}

AFTER:

function ep_this_page_included()
{
	global $post_ID;
	// New post? Do NOT include!
	if ( ! $post_ID ) return false;
	$excluded_ids = ep_get_excluded_ids();
	// If there's no exclusion array, we can return true
	if ( empty($excluded_ids) ) return true;
	// Check if our page is in the exclusion array
	// The bang (!) reverses the polarity [1] of the boolean
	return ! in_array( $post_ID, $excluded_ids );
	// fn1. (of the neutron flow, ahem)
}

Now, new pages do not display in menus by default, but can easily be turned on in their Edit page if you want them to.