The first five categories, in the Manage Categories... dialog box, are displayed in the Media Library area, in the user-defined row. Categories can be moved to and from this display area.
Go to Edit -> Manage Categories... This will open the Manage Categories dialog box.
Click the category that you would like be moved (it should be highlighted).
Move the category up in the listing by clicking the Move Up button until the category is in one of the top five positions. You can move categories to and from the Media Library area with the Move Up and Move Down buttons.
Click the OK button.
View the Media Library area.
Tip: You are able to access all of your categories from the Query drop down menu in the Media Library area.
How to create a new Category
Managing the Media Library categories