A Gantt chart, more commonly known as a bar chart, is a popular way to develop and manage plans. You can display any workflow group as a Gantt chart in OneBox OS, so as manage the tasks: change the time frames right on the chart, change priority, order and subordination.
Technical aspect: Gantt chart is targeted at "planned" field in orders. When you change the date block positions will change in the chart. When you drag the blocks, you are changing the "planned" date in a specific task.