Yes, preferences are not implemented yet. And that includes the ability to customise the keyboard shortcuts. This will come in a following alpha update though.
However, for now, did you notice the Q and W keys? They are an alternative to exactly the up/down arrow keys. And they are better positioned (to the left) on the keyboard if you are using your right hand to draw with.
Check out the keyboard shortcuts for more info. You get to them in the Help menu of Animation Paper.