Solar Bang wrote
Is it possible to make a sub forum private
Yes. At the sub-forum level go to USERS > PERMISSIONS and change the first option from the default, so "anyone" can no longer can view the application. This is certainly true when the top level application is MIXED with FORUM sub-applications. I am less certain about other combinations of applications.
and keep it out of the eye of the search engines, but still have the public (main) forum indexable by the search engines?
There is an option at the top-level of any forum to stop search engines indexing a forum OPTIONS > EDITOR > CHANGE APPEARANCE > Hide contents from search engines. As the change appearance option does not appear on sub-forums, I assume this option is inherited by sub-forums. However, I have to assume that search engine bots are in the "anyone" group, so they will not be able to crawl a hidden sub-forum, regardless of the search engine setting of the top-level forum.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.