UPDATE:
As of v3.1.13, navigation arrows center vertically to the screen regardless of page height (or scaling).
The arrows are no longer part of the anythingSlider object, they're part of the nav element at the root of the HTML body.
You can attach any of the following inside a .css text file using the Resources section the the in5 dialog.
To hide the arrows on smaller screens (just make sure you have swipe enabled or have designed other navigation options):
@media only screen and (max-device-width : 1024px) {
nav#page-nav > button { display:none !important; }
}
To set the arrow to a fixed location:
nav#page-nav > button { top:250px; }
(Replace 250 with the number of your choice)