Messing with the Create New Gallery screen

I’d like to be able to launch the new Create/Insert New Gallery screen from anywhere in the back office and retrieve whatever images a user has picked for his/her new gallery. This is because, in the end, I want the user to pick some images so that their IDs will be stored in some post’s metadata, instead of just inserting a shortcode inside the post’s content.

Now, as WordPress uses Javascript for most of this, my usual method of looking for actions and filters didn’t get me too far. ?? Any advice on this? I haven’t found a lot of docs on the new Media features yet.

Thanks.