you kinda can already, although the above text "utilities" would be a button that is clickable.. (which you could link to do whatever you want, maybe open a folder with more utilities in it)
I attached a screenshot
HOW TO:
click all settings radio button if u havnt
go to customize start menu tab
add new custom item
set its label
create another custom item below it
check "instert sub-items as buttons"
hit ok
create sub items for everything you want to add under it by:
create custom command, drag it right over your new icon, so its nested within
set its link/command/label/icon how you want..
press Ok, and then ok to save settings now test out