Although the gadget does not include an option for configuring the display of categories in a drop-down menu, you can achieve this effect by editing the HTML of your blog design. How to Hide the ...

We can also add drop-down menus to our HTML forms. We can use the select element to implement these drop-down menus. Input choices are in “option” elements as shown in the example below.

When you a create a form, the combo box draws a drop-down menu on a single line, from which users select from a series of preset values. You cannot write in these values when you create the combo box.