Flask-Plugins provides an easy way to create plugins for your application. It is also possible to create Events which can than be used to extend your application without the need to modify your core code.
First you need to install it. It is available on the Python Package Index.
pip install flask-plugins
and then you need to initialize it somewhere in your code.
from flask_plugins import PluginManager
plugin_manager = PluginManager()
it also supports the factory pattern.
from flask_plugins import PluginManager
plugin_manager = PluginManager()
plugin_manager.init_app(app)
The documentation is located here.