If you do /characterconfig, you can customize the number of rows and columns in each hotbar.
If you do /hudlayout, you have four save slots. Each slot saves its own hotbar settings from /characterconfig.
So if you'd like to use different hotbar formats for different jobs, you would set them up in separate HUD layout save slots, then use a macro like this:
(Type /macros in the chat box to open the macro window, then make a macro with the following lines)
Code:/gs change GEARSETNUMBER /hudlayout HUDSAVESLOTNUMBER /micon GEARSETNUMBER gearset
ex, changing to gearset 12 with HUD layout 4:
Code:/gs change 12 /hudlayout 4 /micon 12 gearset