The substitutions window only displays cases of substitution where the absent class or absent teacher is assigned to the currently active department.
Please look at the example in the figure below. Teacher Aristotle is assigned to department EE and class 1a to department ME.
Teacher Aristotle is now set to absent on 20 September. On this day he is due to teach class 1a, as well as class 2b.
If the department drop-down list is set to department EE, all open substitutions will be listed in the substitutions window since the absent teacher Aristotle belongs to this department.
If, on the other hand, department ME is selected, only those substitutions will be displayed where an element of department ME is involved. In our example this is class 1a.
As of Untis 2017 you can show the 'Dept' column in the substitution window via 'Grid adjustment' so that you can see to which department the substitution belongs to.
This way you can also filter two or more departments. No general department drop-down list may be set for this. If you want to see the substitutions of the departments mechanical engineering and electrical engineering, for instance, then enter 'ME|EE' in the filter line.