I have had several folks comment to me during the course of T240490 that the only way for regular but trusted users to discuss things without them being totally publicly is to file them as security issues. That results in some tasks being viewed and managed as security issues, when really they are just confidential conversations etc. I know "Spaces" take care of this for some of our teams where much of their work is sensitive.
We already have https://phabricator.wikimedia.org/maniphest/task/edit/form/23/ but it seems the discoverability on that isn't working out. I'm going to add this to the global drop down and try to surface it elsewhere.