[Kototama]

I put the mouse between the two parts of my Ergodox. It decreases the elbow movements and the tension.

You can also program the keyboard to control the mouse pointer but I found it not practical.

[flurdy]

I overkill. Mostly I have a trackball in the middle as well as an ergonomic Penguin mouse on the side. I rotate and swap between what is on the left, right and middle. A trackball doesn't need a lot of space.