How to customize the designation of the labels?

Double-click in a column to customize the label. For the same modification, you can distinguish what is written on the timetables of the teachers, classes, students, and rooms.
For example, for the absence of a teacher, you can choose to display "Absence" on the teacher's timetable, "Teach. absent" on the timetable of the classes, "Study Hall" on the timetable of the students and "Canceled" on the timetable of the room.