Right now, when you want to add an assignment, but make sure it does not coincide with the deadline of another subject, there is no way to see this for these specific students. You would have to go to the calendar, and see for that year group, what deadlines they have for that day. However, the utility of this is limited because you don't know by memory which classes your students participate in. The ideal solution would be to see within the Assign Settings, numbers highlighted in that small calendar for the days there are conflicts with other tasks. If you would like to see what the conflicts are, you click on it and it opens a a full Student Workload section in which you can see the task, the students who has to deliver it, the class and teacher.