Answer by s_ha_dum for How to disable content pagination?

You can kill the "link pages" functionality in one filter by stripping the nextpage markers out of the post content:

function kill_pages($posts,$qry) { if ($qry->is_single()) {  $posts[0]->post_content = preg_replace( '/<!--nextpage(.*?)?-->/', '',  $posts[0]->post_content ); } return $posts;}add_filter('the_posts','kill_pages',1,2);