When having opened more than five courses or groups the user gets a message that he must close tabs first. This is very confusing and nobody intuitively understands what is going on here.
The primary solution is to allow up to 20 or so tabs if this is feasible regarding the memory usage of a course.
The secondary solution is to maintain a last-recently-use list and dispose the oldest and not used resource in the background when the limit is reached.
The focus here is on solution 1.