You can cancel a lesson without entering an absence by clicking the <Cancelled> button. The cancellation is shown in the respective timetable and in the substitution view. For "Undo", just click the <Cancelled> button once again.
The following examples show spontaneous cancellations of lesson parts.
How to cancel a coupling line
If you click on a coupling line in the details window, and then on the <Cancelled> button, the cancellation only applies for the selected row.
Example: Cancellation of a part of a class
If a class is coupled, click in the "Class" field in the details window and by a double click or by clicking the space key you can change to editing mode. Now you can cancel single classes which means that for those the respective period is cancelled.
Go to "Settings | Miscellaneous | Customise" and check the "Mouse-click activates edit mode" box. If this box is checked, a single mouse click is enough to get to the edit mode in a field.