The shift-time toolbox has a little fork icon in the upper right. Click it and the box gets a little taller and you have a "meal time" edit box.
You can't set the time the meal break begins or ends. Total break time is entered here. For example, if lunch is 30 minutes and people get two 15-minute breaks, you'd enter 60 mins of break time.
The value plays into the tallies. It lets you set the actual begin and end times of the shift but have the tally count work hours only.