Why would you do that, it is already on the panel, Tab 2.

Because I do not see it on Tab 2.  Is there some setting that hides it?

I just looked in Customizer and I do see it there, but they are greyed out.  I do not see the that hidden or diasabled are selected as options.

Look in Inventory Management Options on the Additional tab, if Category 4 Description is blank, then the Category 4 field on the Item Maintenance screen will be hidden.

Per Steve....add a description and the field will appear.  Works for all 4 category fields