Nginx Access Lists
The "Access Lists" feature in Nginx Proxy Manager makes it incredibly easy to work with Nginx to further secure cloud resources, in particular (a) using ngx_http_access_module to limit access to certain apps proxied behind Nginx to certain IP addresses; and (b) using ngx_http_auth_basic_module to add additional password authentication in front of an app. Some nice screenshots in this guide from the-digital-life.com here. It could be a nice thing to copy for the Cloudron admin user interface.
There are some apps in Cloudron that you might use within your organization but feel just a bit too exposed (e.g. lack of 2FA, or in case of project management tools things that you'd really want to run as "locally" as possible even with 2FA) and where using Nginx to add additional access restrictions is preferable. So adding this feature would be incredibly helpful in terms of simplifying pre-existing functionality that can be had via the Nginx config files and providing nice visibility to the per-app restrictions in place via the Cloudron admin user interface.