@PitaJ Thank you for the response. I can explain why I need this in more details. I have a website made using Drupal and I am trying to migrate to nodebb. In the existing site, there are small groups and every group contain a set of people. People in the group have permission to post content inside the group and any user can view the content.
Now there is a bigger group which is a common to all place and this is where almost every users in the website is a member of. So if a smaller group want their content to be promoted to a bigger audience (but still wanted to be part of their smaller group for better content organization), they typically post the content in their small group and share it with the big group so that members of big group also get notified.
I am trying to make a similar setup in nodebb using categories + groups. So there will be a category that is open to all (let`s call it 'global category'), anybody can post in that category, and we expect that lot many users will watch this category. Now there will be another category, let us call it 'small category' and a group 'small group'.Only users in 'small group' can post to 'small category'. So 'small category' acts as the place where 'small group' can organize their content. But some of the content they post there also need to be made part of 'global category' so that the content gets displayed in both the category pages and users watching the 'global category' also gets notified,