how to correctly setup configurations to flask when using Factory Pattern?

I have a problem using config in this way (inside a package)

/project
|   __init__.py
│   run.py
|   manager.py
|
|───.env
├───app
│   │   models.py
│   │   __init__.py
│   |   extensions.py
|
├───instance
|   |   __init__.py
│   |   config.py
#/instance/config.py
import os
import random


class Config(object):
    """Parent configuration class."""
    DEBUG=False
    CSRF_ENABLED = True
    SECRET_KEY= os.urandom(20)
    SQLALCHEMY_DATABASE_URI = os.getenv("URI")
    SQLALCHEMY_TRACK_MODIFICATIONS = False

class DevelopmentConfig(Config):
    """Configurations for Development."""
    DEBUG = True


class TestingConfig(Config):
    """Configurations for Testing, with a separate test database."""
    TESTING = True
    DEBUG = True

class StagingConfig(Config):
    """Configurations for Staging."""
    DEBUG = True


class ProductionConfig(Config):
    """Configurations for Production."""
    DEBUG = False
    TESTING = False


app_config = {
    'development': DevelopmentConfig,
    'testing': TestingConfig,
    'staging': StagingConfig,
    'production': ProductionConfig,
}

and run.py

#/run.py

from .app import create_app
import os


setting=os.getenv("SETTINGS")
myapp = create_app(setting)

print(myapp.config)

so when I want to load e.g DevelopmentConfig class, I got the variable setting parsing .env with value development but flask set everything except the debug and flask_env according to the class DevelopmentConfig. Take a look

(winner) C:\Users\Manuel\Desktop\practica_kiero>flask run
 * Serving Flask app "run:myapp"
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: off

this is the actual value of setting: development
this is the app object config after creation <Config {'ENV': 'production', 'DEBUG': True, 'TESTING': False, 'PROPAGATE_EXCEPTIONS': None, 'PRESERVE_CONTEXT_ON_EXCEPTION': None, 'SECRET_KEY': b'\xae\x9e\xb02\x96\x88\x86C\xb4\xa1\xc8\x85\x94\xff\x95\xb9u\xfc\x9b\x9b', 'PERMANENT_SESSION_LIFETIME': datetime.timedelta(days=31), 'USE_X_SENDFILE': False, 'SERVER_NAME': None, 'APPLICATION_ROOT': '/', 'SESSION_COOKIE_NAME': 'session', 'SESSION_COOKIE_DOMAIN': None, 'SESSION_COOKIE_PATH': None, 'SESSION_COOKIE_HTTPONLY': True, 'SESSION_COOKIE_SECURE': False, 'SESSION_COOKIE_SAMESITE': None, 'SESSION_REFRESH_EACH_REQUEST': True, 'MAX_CONTENT_LENGTH': None, 'SEND_FILE_MAX_AGE_DEFAULT': datetime.timedelta(seconds=43200), 'TRAP_BAD_REQUEST_ERRORS': None, 'TRAP_HTTP_EXCEPTIONS': False, 'EXPLAIN_TEMPLATE_LOADING': False, 'PREFERRED_URL_SCHEME': 'http', 'JSON_AS_ASCII': True, 'JSON_SORT_KEYS': True, 'JSONIFY_PRETTYPRINT_REGULAR': False, 'JSONIFY_MIMETYPE': 'application/json', 'TEMPLATES_AUTO_RELOAD': None, 'MAX_COOKIE_SIZE': 4093, 'CSRF_ENABLED': True, 'SQLALCHEMY_DATABASE_URI': 'mysql+pymysql://usuario:contraseña@localhost/db_01?charset=utf8mb4', 'SQLALCHEMY_TRACK_MODIFICATIONS': False, 'SQLALCHEMY_BINDS': None, 'SQLALCHEMY_NATIVE_UNICODE': None, 'SQLALCHEMY_ECHO': False, 'SQLALCHEMY_RECORD_QUERIES': None, 'SQLALCHEMY_POOL_SIZE': None, 'SQLALCHEMY_POOL_TIMEOUT': None, 'SQLALCHEMY_POOL_RECYCLE': None, 'SQLALCHEMY_MAX_OVERFLOW': None, 'SQLALCHEMY_COMMIT_ON_TEARDOWN': False, 'SQLALCHEMY_ENGINE_OPTIONS': {}}>
 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

So what I'm looking for is to switch quickly through the configurations(using the classes) but also including the DEBUG variable of the class config, no having to add an FLASK_ENV and FLASK_DEBUG to .env that's not my aim. Just modifiying the setting envvar. I thank you in advance for the help.