I have a few suggestions concerning loop mode, which I use a lot. Perhaps some aspects only concern the android version.

1) The looped section should remain grayed out the whole time it's active; it's hard to correctly anticipate the loop point without it.
2) After defining a loop, pressing "play"... doesn't play the loop but the whole chart instead... This is very confusing and unintuitive.
3) When applying changes to the practice mode while a loop is playing, the "play" button flashes to indicate that it must be pressed to apply the changes. But in doing so, it exits loop mode, which it shouldn't.