If you need to create a new base class to appear in class list manager or delete an inessential current class you simply go to classes>actions>edit classes.
Create a class by clicking actions once more and clicking new class.
You can delete classes here by clicking on the red bin icon beside each class.
If you want to rename any of the class names or codes just click on the column and type, this will save automatically. Similarly you can change the year of a class here. This is useful if you find that some base classes are incorrectly assigned or are showing up as 'null'.
Once classes are assigned to a year they will appear in your current timetable>class list manager.