There needs to be another way to set defaults.
Environmental variables do not work for everything on Windows.
For example:
If I do not want any color for INFO level, I cannot set environment variable LOGURU_INFO_COLOR="" because then it's disabled on Windows.
I cannot do:

_defaults.LOGURU_INFO_COLOR = ""

Since logger is already initialized.
Instead, I have to do extremely hacky stuff like:

from loguru import _defaults, logger
from loguru._logger import Level

logger.info('bold')
logger._levels['INFO'] = Level(_defaults.LOGURU_INFO_NO, "", _defaults.LOGURU_INFO_ICON)
logger.info('not bold')

Since Level is a namedtuple, I cannot even modify it in-place

Perhaps a config file or an .ini file as well would be better.