Sorry, I was thinking maybe a beatmap practice where you play a part in a song till you get it down to a science, Using easy mode doesn't cut it for me and using auto doesn't let me get the "Hands-on Practice" I like.
Couldn't you just click edit on the difficulty you want, delete the parts you can play easily, and save it as an unranked practice difficulty? Then you can practice the hard parts and skip the easy parts.