When you have multiple notes selected, it can be hard to then move those notes, without accidentally deselecting, and/or creating new notes. Even if you do grab them, it can be tricky to move them where you want them.

Some apps like xequence, have an up down tab, and a left right tab that you can drag.

Also shift left right by 1 bar, and shift up down by an octave are really useful piano roll features once you have multiple notes selected.