Unable to add Realm style in UI

Hi Anyone faced this issue where log in as admin and trying to add realm style for another realm ? drop down only displays Realms nothing else

You have seen a video or something similar? I remember I saw something like that but I think it was an older version. Never been able to find that menu, I changed everything from config file

Its not a customise install.I have to have custom install ? to make changes to UI seems like quite an effort to create your own build and clone all that. can I not just make changes to base install ?