Some larger projects have what’s called a feature bounty, like others have mentioned $20 is very low for someone not familiar with the codebase to do it, it might be enough for someone already familiar with it (but I seriously doubt it since it involves at least some refactoring of the UI to add a shuffle button). However if more people want that feature they can each contribute a small amount and eventually it would be a value that would justify someone to learn the codebase.

That being said, like someone else pointed out, it seems the app is going through some rewriting, so I wouldn’t expect any new features (especially those involving UI) anytime soon.

Finally there are two issues mentioning shuffle in the GitHub, github.com/jarnedemeulemeester/findroid/…/334 and github.com/jarnedemeulemeester/findroid/…/547 you might want to create an account there and voice your wanting of that feature too, by either adding a thumbs up or a comment explaining why this is important to you.

Good luck, hope you get your shuffle play!