I would love a training mode, similar to the one on the console version of Dance Dance Revolution. Players could select a song and adjust the speed, start, and end section of the song they want to practice. There was an option for "assist" settings where you could turn on an audible clap sound that played for each step you needed to do - helpful if you need to learn the specific rhythm of certain sequences. I can't recall if you had the ability to review a song after you practiced it to see the timing of your steps vs when they should have happened - that would be a great way to see specifically which notes you were either early/late or missed.
My current workaround is to take a video of a playthrough of a specific song, then use a video editor to select the desired portion of the song and adjust the playback speed to learn the slash sequence.