This is a accessibility feature, useful for some devices, such as portable laptops, etc.

Map scrolling currently requires the use of a mouse, or using the GoTo dialog.

A set of 2 keyboard shortcuts, say Ctrl J or Ctrl K (like on AMIDST), and/or 2 zoom in/out buttons in the right hand toolbar with the structure/dimension toggles, would make it possible to zoom in or out without using the mouse scroll wheel. It should zoom the map in or out either at power of 2 or Sqrt(2) or equivalent factor multiple of 2^(1/n).

Potential location for on screen buttons for zooming in or out:

Top right near the "go to origin reset zoom" button.