Hi Ken,
Yes, you will have to revert the changes you made manually. For other scenarios, such as setting the objects to Status = REMOVED, you will have to recreate them entirely as setting the status of objects from REMOVED to ENABLED is not possible. For your scenario of adjusting bids, you may refer to this
guide.
As for the "undo" feature, I cannot further comment regarding it as our team currently does not have information if and when this feature can be made available. Additionally, the AdWords API only mirrors what is available in the AdWords UI. If you can confirm that a similar feature is available via the AdWords UI, then I may be able to file a feature request for it. However, this still does not guarantee whether the said feature can be included in future versions of the AdWords API.
Best regards,
Peter
AdWords API Team