The realms plus UI has no way to backup

See the other new tab on the 3 slot view that says manage realm. That is where backups are shown.

Please try the following:

1. Click on one of the 3 realms in the window

2. A button labeled "Edit World" should appear

3. Click that button to access the settings for that world

4. Use the "Download World" button, or the Backups button to access older saves

Please let us know if that does not work for you.