You may group your articles. Go to my account. Click on groups, you may define your own groups. You assign a hub to a group by dragging your hub into the group.
This will not change the hubpages categories, but it will group your hubs together in your groups for ease of sorting and when you have a hub atached to a group, navigation to other hubs in that group is made possible by the scroll with arrows at the bottom of your hub. A great way to invite your readers to read more of your hubs.