The trackball module has two configurable buttons, mapped by default as left click and right click. Use Agent to remap these buttons and configure your module speed and settings.
The ball housing can accumulate dirt over time, resulting in less precise pointer movement. If it happens, rotate the ring counterclockwise, remove the ball, blow into the ball housing, clean the ball with isopropyl alcohol, put the ball back, and seal the ring.
If you can't rotate the ring with bare hands, you can bend a paperclip, put its end into the two small holes of the ring, and rotate it counterclockwise. Alternatively, you can unscrew the two large screws at the bottom of the module, separate the top and bottom housing, and easily access the ring.
When the Mod layer is active, the ball behaves like a scroll wheel, allowing for vertical and horizontal scrolling.
When the Fn layer is active, the ball behaves like arrow keys, allowing quick movement in text editors.