Solution

Place the code bellow in your theme’s functions.php file.

function pagesColumnsHeader($columns) {
	$columns['pageID'] = __('ID');
	return $columns;
}

add_filter( 'manage_pages_columns', 'pagesColumnsHeader' );

function pagesColumnsRow($columnName, $pageID){
	if($columnName == 'pageID'){
		echo $pageID;
	}
}

add_filter( 'manage_pages_custom_column', 'pagesColumnsRow', 10, 2 );

You might also want to check out how to do this for posts listing and how to do it for categories listing.

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