Call up the profile of the person concerned via the user administration. You can find this in the drop-down menu in the header at the top right. Then find the person using the search bar.
Tap on the tile to open the profile. Click on the little pencil to the right of "Abbreviation".
A pop-up message opens here. At this point you can select the correct abbreviation via the drop-down menu and click on "Save" to finish.
If the desired abbreviation is not available, it must first be entered in the linked timetable program (e.g. Untis, DaVinci, Sdui-Timetable).