in AEM 6.2 the correct way to do what you're trying to do is through "metadata schemas" Here is the doc.
https://docs.adobe.com/docs/en/aem/6-2/author/assets/managing-assets-touch-ui/brandportal/metadata-s...
This would allow you to change the default schemas as well as introduce new ones. Even if you tried to do an overlay of image, application etc it won't work. I do not have an answer on why in this particular instance it's not working for you but have an OOB solution that doesn't require any tinkering.