(Local) World Coordinate System

Here is a quick example demonstrating when to use the World coordinate system.

By default, MeshUP opens up with the Local coordinate system enabled.

Open up any object, especially one that is visually easy to tell when it has been rotated. Rotate the object in X, Y or Z.

Now if you want to rotate in line with the World coordinate axes, where Z is directly up, click on the World toggle on the bottom menu bar. Notice the change to the gimbal.

Moving this rotated object in Z will be one transform operation, whereas in the Local coordinate system this would take multiple transforms in multiple axes to achieve the same result.