In the current implementation of RadGanttView undo/redo functionality is not supported. As this is a new feature request for the control, I recommend logging it in our Feedback Portal
where people can track and vote for it.
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items