WordPress at a glance
function is not described

_insert_into_post_button() WP 1.0

Deprecated in 3.5.0. It is no longer supported and can be removed in future releases. It is recommended to replace this function with the same one.

This was once used to display an 'Insert into Post' button.

Now it is deprecated and stubbed.

No Hooks.

Return

Nothing (null).

Usage

_insert_into_post_button( $type );

Code of insert into post button: wp-admin/includes/deprecated.php VER 5.1.1

<?php
function _insert_into_post_button( $type ) {
	_deprecated_function( __FUNCTION__, '3.5.0' );
}