You can start debugging from the current location in design mode by clicking the icon in Design Studio. This will switch the Robot Editor to debug mode and execute as directly as possible to the location that is current in design mode. When that location is reached, debugging will stop. You can then continue debugging from this location by clicking the icon.
This feature is useful if you just want to debug a part of the robot, like a specific branch or a specific iteration of a loop action.
If Design Studio is already debugging the robot when you press the icon, it will have to restart the debugging before it executes to the location, and it will ask you for permission to do this.