Gutenberg Block Filter Hook Key

I’m wanting to add some functionality to the featured image block in the Gutenberg editor. I’ve got pretty close:

enter image description here

The problem is, I’m unable to select an image, and posts that already had a featured image assigned, are not loading the image in the block.

I think this must be due to the original block object’s key not being set. I’ve tried a random value, the post id, the media post id, ‘render’, ‘thumbnail’, and ‘post-thumbnail’, but no dice. What is ‘my-key’ suppose to be set to? Why is the featured image not loading, and not able to be set and saved?

window.wp.hooks.addFilter(      'editor.PostFeaturedImage',      'myplugin/myhook',      function( original ) {          console.log (original);         return function() {              return (                 window.wp.element.createElement(                      'div',                      { key: 'outer' + Math.random() },                      [                         'Prepend above',                         _.extend( original( {} ), { key: 'my-key' } ),                         'Append below'                      ]                 )             );         }      }  );