I'll be honest, this idea, while well intended, is pretty bad. I get where you're coming from, but requesting a feature like this would take quite a bit of time if you go the drawing route, and would functionally work quite poorly. Writing ideas down for a rhythm game, where all the objects are at certain points in the song, is inefficient and difficult to do in the first place. And drawing ideas down is even worse, where the only use would be for slider art. Best case scenario with drawing (and excluding slider art) is that you make a drawing for each couple of objects every 2 seconds. Introducing a feature like this would most likely be ignored by mappers, and new mappers would use it in the beginning before never touching it again. If you get ideas and want to make sure you don't forget them, just make a new difficulty and put the idea there. I guarantee you it would be faster then writing or drawing, and you're able to put down more information like proper object placement, rhythm choice, and trial and error for the best choices to make with the idea.