There are not hierarchical permissions in NodeBB. If you would like to see hierarchical permissions, you could open an issue on our Github page and request such a feature.
I do believe we have a way of copying permissions between groups, so that could help you out in doing what you want.
I have nodebb setup with mongodb. Whenever I login as admin and go to the plugins page. I see this message in the log. I am not able to install any plugins. Clicking on "Install" doesn't do anything. Please help.