You can use Absence Events Maintenance to set values for multiple absence events where they have the same Absence Type and Reason.
For example, absence events with a type of Unknown have been generated when taking attendance for a group of students. However the students are all participating in a school incursion.

To modify multiple absence events in bulk:

Open the Absence Events Maintenance window. See Absence Events Maintenance window.
Use the Filter drop-down menu to select the type of absence event you want to modify. For example, Unexplained Absence Events.
Select the records that you want to modify from the grid.
In the Apply to selected records area select the Absence Type, Reason and Comment to apply to the records.
Click .
Your selections are applied to the relevant grid records.