This is a nice feature but it's not implemented at the moment because it would lead to bad app design (allowing inconsistencies).
1. Let's say you have scheduled one event per day for a given resource for the next year. When you display the current month in the scheduler and use this (hypothetical) feature to insert a new event in the middle it would shift all events that it knows about - i.e. events until the end of this month. It would leave all events from the following months unshifted.
2. Another thing - you don't want to rely on such a feature to be implemented purely on the client-side (the new dates need to be checked on the server side to prevent invalid input from being processed).
This means you have to re-implement it on the server side anyway. When you have the server-side implementation, you can simply send the updated events back and reload the Scheduler with the same effect.