Hi Pierre,
Thanks for using Mighty Addons. We’re just in the middle of writing brief documentation and will be published soon.
And until then, you can access the Pixabay Extension by:
1. Include an Image element of elementor in your page/post.
2. Set an image by clicking on the Image element
3. Look for Mighty Photos in the Navigation Panel
4. And Voila! Go ahead and use it as you like! 😀
Thanks,
Akash