I don't really see the point of such a thing.
You could just take any of the black hole presets and modify any of the numbers that the user would like.
Its not that hard.
The reason that there's no point is because there's no physical surface on black holes.
The whole point of the "random" button for planets, gas giant's, and stars is because they all have near unlimited possible looks or other things.
But black holes have no surface nor appearance.
Also all black holes look the same and do the same thing.
So a random black hole button would be pointless.
But it would save you a minute or two from making your own custom black hole.