Let's say I have a category at the first level named Exercise Equipment. At the second level I have subcategories: Treadmills, Ellipticals, Pulleys, Benches, etc.

For display purposes only, I would like to segment the Exercise Equipment category into two sections/groups: Cardio and Strength. These two segments would only display in the menu to visually separate the subcategories. They should not be clickable nor have there own pages.

All of my main categories need to be segmented in a similar fashion. Should I use the Menu Group control for this? Or should the segments be second level sections that cannot be navigated to?