Hi,
Add on: go through the below videos, Courses & links too
https://www.youtube.com/watch?v=I_b781oT6a8
https://www.youtube.com/watch?v=MZ0Ihu2QGYY
https://docs.mendix.com/howto8/extensibility/widget-development/
https://www.mendix.com/blog/creating-custom-widgets-mendix/
https://www.mendix.com/videos/kickstart-your-widget-development/
https://www.udemy.com/course/mendix-building-a-pluggable-widgets-with-react-hooks/
https://github.com/mendix/widgets-resources
Thanks
Just search the docs. https://docs.mendix.com/howto/extensibility/create-a-pluggable-widget-one/