According to the logger page, if I set default: error I shouldn’t see anything below that level such as warnings. I have set this and restarted HA, but the warnings are still showing on the warning screen.
You can have logger: settings in multiple places - most common place is your configuration.yaml file. I use a different file to manage my logger settings, and I refer to that file in my configuration.yaml file.
Here is my logging file for your reference. You may have to restart HA after making changes, and note that it will not delete existing messages from your log file.