What you're referring too is formation rank. this will allow you to put different unit it different rows. so you could have your scouts in the front, assault second rank, skim riot 3rd, and arty/support under 4th. Though its kinda buggy and doesn't always work how you want from what I remember messing around with it. under settings> Unit Behaviour > Default States> factory of your choice you can change formation there. you can also space left click a selected unit Icon and get to the default states from the description menu.
