React to your own UI actions, like clicking a button in any app. To do this add a new Tasker profile with the "AutoInput UI Action" condition. Then in the Task do anything you'd like. For example, this can be useful when you know that when you click the Cast button in an app, you'll always want to select the first cast device that shows up. In this case you would simply click the first available cast device with AutoInput in the above mentioned Task.