Hi Shigeki,

I've created ticket CONNECTORS-804 to cover the documentation being out of date.

The work that added the "Override target URL" was done as part of CONNECTORS-574.  Once your page is determined to be a login page, it allows you to override the target URL of that page to a URL of your choosing.  So, for instance, if it is a form, it overrides the form action URL; if it is a link, it overrides the link target; etc.