I have found a few tutorials such as a DigitalApps.co and That Dev Girl explaining how to use
"wp.hooks.addFilter( 'editor.PostFeaturedImage'"... in order to create/replace the content of the featured image button.
However, this doesn't help me very much in what I'm trying to do. I would like to hook into the save image feature, so that when the featured image is selected, I can open a popup allowing the user to edit the background positioning of this image.
I already finished the code allowing the user to edit the background positioning and save to the post's meta, just need to know when and which image has been selected. Am I on the right path with the above filter? Can someone please point me in the right direction?