It is on the web app. https://support.plex.tv/articles/200289266-editing-libraries/
But you are only able to access this if this is your own plex server. If you are only accessing a server which has been shared with you, you cannot access this page.
That is the recommended one. So that should be fine.
There is currently something in flux with the Home page and with Recently Added in particular. So this issue might be obsolete with the next server update. For the time being, I’d try to use one of the other desktop apps, as they are more powerful and lighter on the server anyway:
