Replace component
In this selection you can Replace a component of the current course, and when enabled, also Add a new component or Remove an existing component. When in Courses window, you can first double-click to see all components attached to the course, and then either right-click to show the pop-up menu or click [F5] to invoke Component Replace window.
This window displays the possible actions that are permitted to do with the current component (without the risk of causing conflicts). The component that is about to replace the old component or to be added is always of the same category as the current component (a teacher can be replaced by another teacher and so on).
Conflicts (when enabled) shows conflicting components (those that are not displayed) and the locations of conflicts
See the selection Options|Maximum weekly load to find the components and weeks having most of the lectures per week and which will most probably prevent assigning of lectures into timetables.