Starting from version 1.6, every action in Taskheat is undoable.
You can use the Edit ▸ Undo/Redo menu or keyboard shortcut to undo or redo previous actions in the Mac version.
The default shortcut for undo/redo on iPad is a horizontal three-finger swipe. It is recommended for all applications to adopt it, and Taskheat is not an exception.
Shake the device to revert the last operation on iPhone. It will display the confirmation alert where you can confirm what exactly you are going to undo or redo.