Let’s say you had an action to “Phone: Bob about TPS report.” If you phoned Bob and left a message, you’ll likely want to create a new action to reflect that you’re waiting for a response.
This plug-in automatically marks the action complete and creates a duplicate “waiting” action. With a minor addition (documented on the plug-in page), it can also apply a tag of your choice to the duplicate action. Consider assigning a keyboard shortcut to make it even quicker and more convenient.
Autocar (Complete and Await Response) is a more advanced plug-in with similar functionality, adding automatic naming, tagging, and extensive customization.