For those of you who had big frustrations deleting components or sets of components accidentally in the web UI builder, your frustrations and pains are a thing of the past. With this release comes the powerful feature to undo and redo in the web UI builder. If you are accidentally mistaken (deleting the wrong component for example), this feature will help you out.
The undo and redo buttons are placed at the bottom left (above the device switcher). The undo button reverts the effects of the latest action that was executed. If that was a delete action to a component, that means that the delete is reverted. The redo button reverts the effects of the undo action. In this case, it means that the delete will be executed again.