You may create categories for various objects but you can only modify or delete them using the "Manage Categories" item in the tools menu. This will bring up the "Manage Categories" Dialog shown below:
Select the type of category you would like to work on. The category list will fill in with all current categories for this type. You may select a category from the list and all its details will be filled in on the right. You may modify any item. Press the save changes once finished.
You may press "Delete" after selecting a procedure which will delete it from the list.
Pressing the "Add New" button will allow you to create a new category. Fill in all appropriate information after pressing "Add New" and make to press "Save Changes" when done.
Press the "Close" button when you have finished modifying categories.